- Platinum nanofilm formation by EC-ALE via redox replacement of UPD copper: Studies using in-situ scanning tunneling microscopy
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The growth of Pt nanofilms on well-defined Au(111) electrode surfaces, using electrochemical atomic layer epitaxy (EC-ALE), is described here. EC-ALE is a deposition method based on surface-limited reactions. This report describes the first use of surface-limited redox replacement reactions (SLR3) in an EC-ALE cycle to form atomically ordered metal nanofilms. The SLR 3 consisted of the underpotential deposition (UPD) of a copper atomic layer, subsequently replaced by Pt at open circuit, in a Pt cation solution. This SLR3 was then used a cycle, repeated to grow thicker Pt films. Deposits were studied using a combination of electrochemistry (EC), in-situ scanning tunneling microscopy (STM) using an electrochemical flow cell, and ultrahigh vacuum (UHV) surface studies combined with electrochemistry (UHV-EC). A single redox replacement of upd Cu from a PtCl42- solution yielded an incomplete monolayer, though no preferential deposition was observed at step edges. Use of an iodine adlayer, as a surfactant, facilitated the growth of uniformed films. In-situ STM images revealed ordered Au(111)-(√3 × √3)R30°-iodine structure, with areas partially distorted by Pt nanoislands. After the second application, an ordered Moire pattern was observed with a spacing consistent with the lattice mismatch between a Pt monolayer and the Au(111) substrate. After application of three or more cycles, a new adlattice, a (3 × 3)-iodine structure, was observed, previously observed for I atoms adsorbed on Pt(111). In addition, five atom adsorbed Pt-I complexes randomly decorated the surface and showed some mobility. These pinwheels, planar PtI4, complexes, and the ordered (3 × 3)-iodine layer all appeared stable during rinsing with blank solution, free of I- and the Pt complex (PtCl42-).
- Kim, Youn-Geun,Kim, Jay Y.,Vairavapandian, Deepa,Stickney, John L.
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- Cr(III) oxidation with lead dioxide-based anodes
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A procedure for preparing PbO2-based electrodes with a titanium substrate is proposed. A platinum underlayer is first deposited on Ti by metal organic chemical vapor deposition (MOCVD), followed by the electrodeposition of the PbO2 layer. The prepared Ti/Pt/PbO2 anodes were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD) before being used for oxidation of Cr(III) in sulphuric acid. The current efficiency was determined for that electrodes and the results were compared with those obtained with Pb/PbO2 and Ebonex/PbO 2 electrodes with different pH conditions. The Ti/Pt/PbO2 were found to have a very good electrochemical behaviour (current efficiency: φ=0.93 for pH 2), and may be used as dimensionally stable anodes for the oxidation of Cr(III).
- Devilliers,Dinh Thi,Mahé,Le Xuan
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- High-resolution in situ and ex situ TEM studies on graphene formation and growth on Pt nanoparticles
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The formation of graphene layers on MgO-supported Pt nanoparticles was studied by both in situ and ex situ high-resolution transmission electron microscopy (HRTEM). The HRTEM images indicate that graphene sheets grow from steps in the surface of Pt nanoparticles. The subsequent morphology of the graphene sheets is a strong function of Pt particle size. For particles less than ～6 nm in diameter, the graphene sheets form nanotubes or move from the surface of Pt particles and accumulate on the MgO support. Complete particle envelopment by multiple graphene layers was only observed for particle greater than ～6 nm in diameter. The observed dependence of graphene morphology on Pt nanoparticle size and shape is associated with the strain energy generated between graphene layers during their growth and the overall free energy of the graphene-Pt system.
- Peng, Zhenmeng,Somodi, Ferenc,Helveg, Stig,Kisielowski, Christian,Specht, Petra,Bell, Alexis T.
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- Effects of humidity on the performance of ionic polymer-metal composite actuators: Experimental study of the back-relaxation of actuators
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This article focuses on the dependence of water uptake on the displacement, velocity, mechanical force, and charging profiles of perfluorinated ionomer-platinum/Li+-based actuators. Both the displacement and force generation were found to be strongly dependent on the humidity. The primary reason for this effect is a decrease in the stiffness as a result of the humidity. The actuators demonstrated a dramatic reverse motion and a negative force, and this subsequent relaxation was dramatically decreased by decreasing humidity. This relaxation process can be explained by the slow diffusion of water into the elastically softened anode and out of the stiffened camode. There are no clear inflection points on the charging profile during me reverse relaxation, and this suggests that the relaxation process does not involve a major redistribution of counter cations. An increase in water uptake resulted in an enhancement of the velocity of the displacement. A continuous generation of force was also examined by scanning potential, and the force was proportional to the potential. Humidities near 50-60% (i.e., water uptakes of ca. 5 wt %) gave a better actuator bending performance.
- Shoji, Eiichi,Hirayama, Daisuke
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- Fabrication and evaluation of platinum/diamond composite electrodes for electrocatalysis: Preliminary studies of the oxygen-reduction reaction
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A catalytic electrode was prepared using a new electrically conducting and corrosion resistant carbon support material, boron-doped diamond. Fabrication of the composite electrode involves a three-step process: (i) continuous diamond thin-film deposition on a substrate, (ii) electrodeposition of Pt catalyst particles on the diamond surface, and (iii) short-term diamond deposition to entrap the metal particles into the surface microstructure. The process results in a conductive, morphologically, and microstructurally stable composite electrode containing metal particles of somewhat controlled composition, size, and catalytic activity. The metal catalyst particles were galvanostatically deposited from a K2PtCl6/HClO4 solution, with the metal particle size (50-350 nm) and distribution (～109 cm-2) being controlled by adjusting the galvanostatic deposition and secondary diamond-growth conditions. For a 300 s Pt deposition time, the estimated loading was 75.8 μg/cm2, assuming a 100% current efficiency. The composite electrode was extremely stable, both structurally and catalytically, during a 2 h polarization in 85% H3PO4 at 170°C and 0.1 A/cm2. The electrode's catalytic activity was evaluated using the O2 reduction reaction at room temperature in 0.1 M solutions of H3PO4, H2SO4, and HClO4. The kinetic parameters (Tafel slope and exchange current density) were obtained by cyclic voltammetry and were found to be comparable to those for a polycrystalline Pt electrode in the same media. Tafel slopes of -63 to -80 mV/dec were observed at low overpotentials, with the lowest slope in HClO4 and highest in H3PO4. The exchange current density ranged from 10-12 to 10-10 A/cm2, and increased in the order of H3PO4 2SO4 4. The potential advantages of the composite electrode, as compared with commercial sp2 carbon electrodes, are (i) the corrosion resistance of the diamond support, resulting in highly stable reaction centers at high potentials, current densities, and temperatures, and (ii) the fact that all of the catalyst particles are strongly anchored at the film surface and are not contained inside pores.
- Wang, Jian,Swain, Greg M.
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- Synthesis, characterization of FAU/EMT intergrowths and its catalytic performance in n-pentane hydroisomerization reaction
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Zeolites FAU, EMT and their intergrowths were synthesized using 15-crown-5, 18-crown-6 and their equimolar mixture, respectively. The synthesized products were characterized by XRD, SEM-EDX, N2 adsorption and TPD-NH3. The solids obtained were all highly crystalline. The FAU samples were formed by octahedral submicrometric crystallites, EMT samples had hexagonal plate morphology of 2-5 μm. The intergrowth crystals were micrometric hexagonal plates through whose hexagonal faces, the octahedral FAU crystallites intergrow. The intergrowth proportion was evaluated by means of DIFFaX, resulting in different intergrowth proportions, depending on the molar ratio of template/Al2O3 and on the relative template proportion used in the synthesis gel. For a template/Al2O3 ratio of 0.70, a 50%FAU/50%EMT intergrowth proportion was obtained, with cluster-type stacking and for template/Al2O3 of 0.30 the intergrowth proportion was 12%FAU/88%EMT with two stacking arrangements: clusters and random. Platinum was incorporated to these zeolites and their intergrowths by solid ion exchange; the metal dispersion was evaluated by TEM. For most catalysts the platinum particles were between 4 and 10 nm. All the catalysts were active for n-pentane conversion. The activity was found to be a function of acidity. The intergrowth catalysts were the most active materials. The iso-pentane selectivity, at 350 °C and carrier gas composition of H2:N2 = 2:1, was 82% independent of time on stream, acidity, Pt/Al ratio and Pt dispersion. The selectivity increased with decreasing temperature and as carrier gas composition became richer in H2. The catalytic remaining activity (at 10 min) decreased in the following order: FAU > EMT > intergrowth.
- Belandría,Gonzàlez,Aguirre,Sosa,Uzcátegui,González,Brito,González-Cortés,Imbert
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- Temperature effect on the electrode kinetics of ethanol oxidation on Pd modified Pt electrodes and the estimation of intermediates formed in alkali medium
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Ethanol has been recognized as the ideal fuel for direct alcohol fuel cell (DAFC) systems due to its high energy density, non-toxicity and its bio-generation. However the complete conversion of ethanol to CO2 is still met with challenges, due t
- Mahapatra,Dutta,Datta
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- Platinum Electroless Deposition on Silicon from Hydrogen Fluoride Solutions: Electrical Properties
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Current transport through mesa structures formed by Pt electroless deposition on p-Si wafers has been studied. The silicon treatment in the solution of sodium chloroplatinate in dilute HF acid is shown to result in both Pt nucleation on the Si surface (cathodic process) and Si wafer etching by fluoride ions (anodic process). These processes occurred simultaneously, forming the developed Pt/Si interface. Auger electron spectroscopy and C-V curves reveal the formation of a dielectric interface layer between Pt and Si of hundreds of nanometers that extends with the time of treatment. The electrical properties of mesa structures exhibit Schottky barrier behavior. Both conditions of current transport along the deposited layer and parameters of Schottky contact are defined vs. the deposition time and compared with that for thermally deposited Pt contact.
- Kuznetsov,Skryshevsky,Vdovenkova,Tsyganova,Gorostiza,Sanz
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- In situ FTIR spectroscopic studies of (bi)sulfate adsorption on electrodes of Pt nanoparticles supported on different substrates
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Nanostructured Pt electrodes were prepared by electrodeposition of Pt nanoparticles on different substrates (GC, Pt and Au) under cyclic voltammetric conditions and with various number (n) of potential cycling, and were denoted as nm-Pt/S(n) (S = GC, Pt and Au). Adsorption of (bi)sulfate on the nm-Pt/S(n) was studied by in situ FTIR reflection spectroscopy. It has been revealed that the nanostructured Pt electrodes exhibit anomalous IR properties for (bi)sulfate adsorption regardless of the different reflectivity of substrate, i.e. the IR absorption of (bi)sulfate species adsorbed on all the nm-Pt/S(n) electrodes is significantly enhanced and the IR band direction is completely inverted in comparison with the same species adsorbed on a bulk Pt electrode. The two IR bands around 1200 and 1110 cm-1 attributed to adsorbed (bi)sulfate species are shifted linearly with increasing electrode potential, yielding Stark tuning rates (d over(ν, ?) / d ES) of 152.1 and 21.1 cm-1 V-1 on nm-Pt/GC(20), respectively. Along with increasing n, the Stark tuning rate of the IR band around 1200 cm-1 decreases quickly and declined to 7.6 cm-1 V-1 on nm-Pt/GC(80), while the Stark tuning rate of the IR band near 1100 cm-1 is fluctuated between 23.0 and 16.2 cm-1 V-1. It has determined that the enhancement of IR absorption of (bi)sulfate adsorbed on nanostructured Pt electrode is varied with substrate material and n, and a maximal 16-fold enhancement of the IR band near 1200 cm-1 has been measured on the nm-Pt/GC(30) electrode. The in situ FTIR studies illustrated that the adsorption of (bi)sulfate occurs mainly in the double layer potential region, and reaches a maximum around 0.80 V. The results demonstrated also that the competitive adsorption of CO and oxygen species can inhibit completely (bi)sulfate adsorption, which has evidenced a weak interaction of (bi)sulfate with nm-Pt/S(n) electrode surface.
- Zeng, Dong-Mei,Jiang, Yan-Xia,Zhou, Zhi-You,Su, Zhang-Fei,Sun, Shi-Gang
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- Recovery of platinum with calcium oxide sorbent in ammonia oxidation
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The reaction of granulated CaO sorbent with platinum lost in high-temperature oxidation of ammonia was studied. Physicochemical properties of the product and conditions and mechanism of its formation are considered.
- Zakharchenko
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- Light-driven synthesis of hollow platinum nanospheres
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Hollow platinum nanospheres that are porous and have uniform shell thickness are prepared by templating platinum growth on polystyrene beads with an adsorbed porphyrin photocatalyst irradiated by visible light. The Royal Society of Chemistry.
- Garcia, Robert M.,Song, Yujiang,Dorin, Rachel M.,Wang, Haorong,Li, Peng,Qiu, Yan,Van Swol, Frank,Shelnutt, John A.
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- Porous platinum mesoflowers with enhanced activity for methanol oxidation reaction
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Porous Pt and Pt-Ag alloy mesoflowers (MFs) with about 2 μm in diameter and high porosity were synthesized using Ag mesoflowers as sacrificial template by galvanic reaction. The silver content in Pt-Ag alloys can be facilely controlled by nitric acid treatment. And the pure Pt MFs can be obtained by selective removal of silver element from Pt72Ag28 MFs electrochemically. Both Pt45Ag55, Pt72Ag 28 and pure Pt show a high catalytic performance in methanol oxidation reaction (MOR). Especially, pure Pt MFs exhibited a 2 to 3 times current density enhancement in MOR compared with the commercial used Pt black, which can be attributed to their porous nanostructure with 3-dimentional nature and small crystal sizes.
- Zhuang, Lina,Wang, Wenjin,Hong, Feng,Yang, Shengchun,You, Hongjun,Fang, Jixiang,Ding, Bingjun
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- Promotion effects in the oxidation of CO over zeolite-supported Pt nanoparticles
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Well-defined Pt-nanoparticles with an average diameter of 1 nm supported on a series of zeolite Y samples containing different monovalent (H+, Na+, K+, Rb+, and Cs+) and divalent (Mg2+, Ca2+, Sr2+, and Ba2+) cations have been used as model systems to investigate the effect of promotor elements in the oxidation of CO in excess oxygen. Time-resolved infrared spectroscopy measurements allowed us to study the temperature-programmed desorption of CO from supported Pt nanoparticles to monitor the electronic changes in the local environment of adsorbed CO. It was found that the red shift of the linear Pt-coordinated Ca??O vibration compared to that of gas-phase CO increases with an increasing cation radius-to-charge ratio. In addition, a systematic shift from linear (L) to bridge (B) bonded Ca??O was observed for decreasing Lewis acidity, as expressed by the Kamlet-Taft parameter ?±. A decreasing ?± results in an increasing electron charge on the framework oxygen atoms and therefore an increasing electron charge on the supported Pt nanoparticles. This observation was confirmed with X-ray absorption spectroscopy, and the intensity of the experimental Pt atomic XAFS correlates with the Lewis acidity of the cation introduced. Furthermore, it was found that the CO coverage increases with increasing electron density on the Pt nanoparticles. This increasing electron density was found to result in an increased CO oxidation activity; i.e., the T50% for CO oxidation decreases with decreasing a. In other words, basic promotors facilitate the chemisorption of CO on the Pt particles. The most promoted CO oxidation catalyst is a Pt/K-Y sample, which has a T50%of 390 K and a L:B intensity ratio of 2.7. The obtained results provide guidelines to design improved CO oxidation catalysts. ? 2005 American Chemical Society.
- Visser, Tom,Nijhuis, T. Alexander,Van Der Eerden,Jenken, Karin,Ji, Yaying,Bras, Wim,Nikitenko, Sergei,Ikeda, Yasuo,Lepage, Muriel,Weckhuysen, Bert M.
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- Structure and morphology of catalysts produced via oxidation of Mo-Pt alloys
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A novel approach has been proposed for producing platinum-containing catalysts via oxidation of molybdenum-platinum powders. The effect of alloy composition on the structure and morphology of the oxidation products has been studied by a variety of physico
- Nesterenko,Meshkov,Zosimova,Nesterenko
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- Pt-Ru electrodeposited on gold from chloride electrolytes
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Voltammetric behavior of submicron-thick electrodeposited Pt-Ru on gold support is studied in sulfuric acid solution as a function of deposition potential and Pt:Ru ratio in chloride bath. In contrast to Pt-Ru, deposition of pure Ru is observed only at potentials of hydrogen evolution. The reason is found to be of kinetic nature, namely an inhibition of Ru deposition in presence of chloride. Chloride ions remain adsorbed on Ru at more negative potentials than on Pt and Au because of more negative ruthenium potential of zero free charge. Cu-UPD is applied to test the surface content of the oxidized Ru on pure Ru and various Pt-Ru surfaces. An enhancement of Ru oxohydroxides reduction in presence of Pt is observed. The electrocatalytic activity of Pt-Ru in respect to methanol oxidation correlates with the content of rechargeable surface Ru oxide. Ageing and 'training' of Pt-Ru electrodeposits under various modes is studied in order to determine the conditions of irreversible Ru oxidation. No manifestations of Ru dissolution from Pt-Ru electrodeposits in 0.5 M H2SO4 are found for anodic potential limits up to 1.1 V (RHE), in agreement with thermodynamic predictions. Electrodeposited Pt-Ru can be considered as a convenient model system for the study of Ru dissolution and crossover, as well as for determining the nature of the active surface species in the real composite catalysts for methanol oxidation.
- Gavrilov,Petrii,Mukovnin,Smirnova,Levchenko,Tsirlina
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- Rational synthesis of Pt spheres with hollow interior and nanosponge shell using silica particles as template
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Here we report a facile and efficient method to prepare Pt spheres with hollow interior and nanosponge shell with high surface area. Such a unique Pt nanostructure can effectively improve the electrocatalytic performance of Pt catalysts by facilitating the access of electroactive species to the full-extent Pt surface. The Royal Society of Chemistry.
- Ataee-Esfahani, Hamed,Nemoto, Yoshihiro,Wang, Liang,Yamauchi, Yusuke
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- Platinum concave nanocubes with high-index facets and their enhanced activity for oxygen reduction reaction
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Many facets: A simple synthetic route, which is based on reduction in aqueous solution, results in Pt concave nanocubes (see picture) enclosed by high-index facets such as {510}, {720}, and {830}. The nanocrystals exhibit electrocatalytic activity (per un
- Yu, Taekyung,Kim, Do Youb,Zhang, Hui,Xia, Younan
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- Kinetic studies of the stability of Pt for NO oxidation: Effect of sulfur and long-term aging
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The stability of Pt catalysts for NO oxidation was analyzed by observing the effect of pre-adsorbed sulfur on the reaction kinetics using a series of Pt/SBA-15 catalysts with varying Pt particle sizes (ca 2-9 nm). Our results indicate that sulfur addition did not influence catalyst deactivation of any of the Pt catalysts, resulting in unchanged turnover rates (TOR) and reaction kinetics. The presence of sulfur on Pt was confirmed by X-ray absorption fine structure spectroscopy (EXAFS) under reducing environments. However, exposure of the catalyst to NO oxidation conditions displaced sulfur from the first coordination shell of Pt, yielding Pt-O bonds instead. Re-reduction fully recovered the Pt-S backscattering, implying that sulfur remained near the Pt under oxidizing conditions. X-ray photoelectron spectroscopy (XPS) and chemisorption measurements confirmed the presence of sulfur near platinum. The invariance of the NO oxidation reaction to sulfur poisoning is explained by sulfur displacement to interfacial sites and/or sulfur binding on kinetically irrelevant sites. Formation of Pt oxides remains as the main source of catalyst deactivation as observed by kinetic and X-ray absorption spectroscopy (XAS) measurements.
- Pazmino, Jorge H.,Miller, Jeffrey T.,Mulla, Shadab S.,Nicholas Delgass,Ribeiro, Fabio H.
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- Layered double hydroxides supported nanoplatinum catalyst for Suzuki coupling of aryl halides
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Layered double hydroxides (LDH) supported nanoplatinum catalyst was prepared and employed for Suzuki cross coupling of aryl halides (iodides and bromides) with a broad range of arylboronic to afford the corresponding biaryls in good to excellent yields without using any external ligand. The catalyst is reused for several cycles with consistent activity.
- Choudary, Boyapati M.,Roy, Moumita,Roy, Sarabindu,Kantam, M. Lakshmi
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- Gas-phase kinetics of ground-state platinum with O2, NO, N2O and CH4
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The gas-phase reactivity of ground-state platinum with O2, NO, N2O and CH4 is reported. Platinum atoms were produced by the photodissociation of [Pt(CH3)3(C5H4CH3)] and detected by laser-induced fluorescence. The reaction rates of platinum with all the reactants are pressure dependent indicating adduct formation; however, the reaction with N2O has a bimolecular component. The room-temperature limiting low-pressure third-order rate constants in argon buffer are (2.3 ± 0.2) × 10-31 molecule-2 cm6 s-1, (4.3 ± 0.4) × 1031 molecule-2 cm6 s-1, (3.7 ± 0.5) × 10-31 molecule-2 cm6 s-1 and (2.1 ± 0.9) × 10-28 molecule-2 cm6 s-1 for O2, NO, N2O and CH4, respectively, where the uncertainties are ±2σ. The limiting high-pressure second-order rate constants are (2.5 ± 0.5) × 10-12 molecule-1 cm3 s-1, (2.3 ± 0.8) × 10-11 molecule-1 cm3 s-1, (2.3 ± 0.3) × 10-12 molecule-1 cm3 s-1 and (6.3 ± 0.3) × 10-12 molecule-1 cm3 s-1 for O2, NO, N2O and CH4, respectively. The second-order rate constant for the abstraction channel for the reaction with N2O at 296 K is approximately 1 × 10-13 molecule-1 cm3 s-1.
- Campbell, Mark L.
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- Electrochemical properties of Pt coatings on Ni prepared by atomic layer deposition
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Presented herein is an approach to fabrication of Pt coatings on non-noble metals with (sub)monolayer thickness. The Pt coatings were prepared using atomic layer deposition (ALD) in which Ni-disk substrate is exposed to MeCpPt Me3 and H2 in alternating cy
- Hoover, Robert R.,Tolmachev, Yuriy V.
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- Integrated structural control of cage-type mesoporous platinum possessing both tunable large mesopores and variable surface structures by block copolymer-assisted Pt deposition in a hard-template
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Cage-type mesoporous Pt with tunable large mesopores possessing smooth and rough pore surfaces were prepared selectively by the deposition of Pt in the absence and presence of a block copolymer in a hard-template, respectively. The Royal Society of Chemistry 2010.
- Kuroda, Yoshiyuki,Yamauchi, Yusuke,Kuroda, Kazuyuki
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- Support effects on the oxidation of ethanol at Pt nanoparticles
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The effects of metal oxide supports on ethanol oxidation have been investigated by drop coating Pt nanoparticles onto glassy carbon electrodes coated with thin layers of ruthenium oxide, tin oxide, a mixed Ru + Sn oxide, and onto an indium-tin oxide (ITO) electrode. All four oxide supports exhibited significant co-catalytic effects, with their effectiveness at low potentials increasing in the order Ru oxide ITO Ru + Sn oxide Sn oxide. However, at higher potentials (e.g. 0.4 V vs. SCE) currents were higher for Pt supported on Ru oxide or Ru + Sn oxide than on Sn oxide, revealing mechanistic differences between the roles of Ru and Sn oxide. Although Sn oxide produced very high initial activities, ITO and Ru + Sn oxide provided more stable performances.
- Moghaddam, Reza B.,Pickup, Peter G.
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- Pulsed galvanostatic deposition of Pt particles on microcrystalline and nanocrystalline diamond thin-film electrodes I. Characterization of as-deposited metal/diamond surfaces
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The pulsed galvanostatic deposition of nanometer-sized Pt particles on electrically conducting microcrystalline and nanocrystalline diamond thin-film electrodes is reported. The deposition was studied as a function of pulse number (10-50) and current density (0.50-1.50 mA cm-2) at the two morphologically different forms of diamond. The deposition of catalyst particles using ten 1 s pulses (duty cycle 50%) at a current density of 1.25 mA cm -2 (geometric area) produced the smallest nominal particle size and the highest particle coverage on both diamond surfaces. Secondary electron micrographs revealed metal particle deposition over much of the diamond surface, a nominal particle size of 43 ± 27 nm [relative standard deviation (RSD) = 63%] for microcrystalline and 25 ± 25 nm (RSD = 100%) for nanocrystalline diamond, and a nominal particle coverage of 7.5 (±0.9) × 109 cm-2 for microcrystalline and 1.9 (±1.0) × 1010 cm-2 for nanocrystalline diamond. Deposition under these conditions resulted in the most efficient utilization of the metal catalyst for H+ adsorption, based on the electrochemically active Pt area normalized to the estimated metal loading. Typical specific surface areas of 10-50 m2/g Pt were calculated, which compare favorably to values obtained at sp2 electrodes, like carbon and graphite. The influence of the diamond electrode microstructural and electronic properties on the formation of dimensionally uniform metal adlayers is discussed.
- Bennett, Jason A.,Show, Yoshiyuki,Wang, Shihua,Swain, Greg M.
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- A general strategy for preparation of Pt 3d-transition metal (Co, Fe, Ni) nanocubes
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A facile, reliable, general, and robust synthetic method for preparation of high-quality, (100)-terminated Pt3M nanocubes (M = Pt or 3d-transition metals Co, Fe, and Ni) has been developed. It was identified that addition of W(CO)6 i
- Zhang, Jun,Fang, Jiye
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- Area-selective atomic layer deposition of platinum on YSZ substrates using microcontact printed SAMs
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Using (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe3) and oxygen as precursors, Pt has been deposited by atomic layer deposition (ALD) on the surfaces of yttria-stabilized zirconia (YSZ), a solid oxide electrolyte, as well as on oxide-covered silicon. Ex situ analyses have been carried out to examine the properties of both as-deposited and postannealed Pt films. X-ray photoelectron spectroscopy measurements demonstrate that there are no detectable impurities in the as-deposited Pt films, and four-point probe measurements show that the resistivity for a 30.2 nm film is as low as 18.3 μ cm. The use of area-selective ALD to deposit patterned Pt has also been investigated. By coating these same substrates with octadecyltrichlorosilane (ODTS) self-assembled monolayers (SAMs), Pt ALD can be successfully blocked. Furthermore, it is shown that by transferring the ODTS SAMs to the substrates by microcontact printing (μCP) using patterned stamps, platinum thin films are grown selectively on the SAM-free surface regions. Features with sizes as small as 2 μm have been deposited by this combined ALD-μCP method; the resolution is limited by the printed pattern and, likely, can be achieved at dimensions significantly smaller than a micrometer.
- Jiang, Xirong,Bent, Stacey F.
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- Microgravity effects on the electrochemical oxidation of ammonia: A parabolic flight experiment
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The diffusion of molecular species through nanoporous systems in microgravity conditions is of interest due to the implications of nanotechnology in aerospace technologies. Herein we present the electrochemical oxidation of ammonia at Pt nanoparticles/nano-supporting electrode systems. The decomposition of ammonia has become of critical importance since it is a common component in aqueous streams. The experiments were carried out in a parabolic flight by using different materials to test the electrooxidation of ammonia. Linear polarization curves were attained in microgravity for all materials. In general, a reduction in catalytic performance of 20-65% was observed.
- Nicolau, Eduardo,Poventud-Estrada, Carlos M.,Arroyo, Lisandra,Fonseca, José,Flynn, Michael,Cabrera, Carlos R.
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- Addition of Hydroxide, Alkoxide, and Carboxylate Anions to Platinum-bonded Ethylene
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The cation 2-C2H4)Cl(tmen)>+ (1) (tmen=N,N,N',N'-tetramethylethylenediamine) reacts with water and alcohol under basic conditions to give nucleophilic addition of hydroxide and alkoxide anions to ethylene and formation of (4) and respectively.Compound (4), either in solution or in the solid, undergoes a condensation reaction with formation of (5).Compound (1) reacts also with excess of acetate in water to give the ester complex Cl(tmen)> (6).Compound (6), in the solid state, slowly dissociates to acetate anion and cation (1), redissolution in chloroform restoring the original species.Compounds (3)-(6), dissolved in methanol, are transformed into (2).
- Fanizzi, Francesco P.,Intini, Francesco P.,Maresca, Luciana,Natile, Giovanni,Gasparrini, Francesco
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- Photosensitised Oxidation of Water by CdS-based Suspensions
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Dispersions of CdS powder with or without metal or metal oxide deposits, such as Pt, Au, Ag, Rh, Rh2O3 and RuO2, have been used to sensitise the oxidation of water by PtCl62-.The most active of the CdS-based photosensitisers was found to be one in which Pt was deposited by precipitation of a Pt colloid onto the surface of a CdS sample which had been annealed in air for 3 h prior to platinisation.A study was made to determine the optimum conditions for O2 evolution.The initial rate of O2 evolution was found to depend upon a number of factors including: pH, , 2->, , Pt loading and CdS annealing temperature and environment.Altough a number of different electron acceptors were tried, including PtCl62-, PtCl42-, Pt(OH)62-, H2AuO3-, S2O82-, Co(NH3)5Cl2+ and Fe(CN)63-, O2 photogeneration was observed with only PtCl62- and Fe(CN)63-.A number of other materials were tested as photocatalysts for the oxidation of water by PtCl62-, including TiO2, TiO2/Pt, TiO2/Rh2O3, CdO, CdO/Pt, HgS/Pt, SiO2/Rh2O3 and Al2O3/Pt; howewer, only the TiO2-based materials showed any activity.The results of this work are discussed with respect to the current controversy over the mechanism for O2 evolution.
- Mills, Andrew,Williams, Geraint
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- Oxygen reduction at platinum modified gold electrodes
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The reduction of oxygen has been studied on polycrystalline gold electrodes modified by platinum deposited spontaneously from an aqueous K 2PtCl6 solution via the displacement of copper or lead adlayers. The change in the surface composition and morphology has been checked by XPS, AES and AFM data. The kinetic results have shown that such electrodes may present a higher catalytic activity compared to bulk platinum electrodes during a scan where the potential is made more positive and is thus clearly expressed by an hysteresis in the CV curves. The displacement of copper and lead deposits gave similar amplitudes of the hysteresis but the modified electrodes obtained via a lead deposit present a better stability upon cycling in acid solutions. The observed behaviour can be correlated to the modification of the M-OH formation and reduction on noble metals.
- Van Brussel,Kokkinidis,Hubin,Buess-Herman
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- Synthesis and X-ray crystal structures of bis(oxazolinyl)phenyl-derived chiral palladium(II) and platinum(II) and -(IV) complexes and their use in the catalytic asymmetric aldol-type condensation of isocyanides and aldehydes
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The transmetalation of (Phebox)SnMe3 (3; Phebox = 2,6-bis(oxazolinyl)phenyl) with PdCl2(PhCN)2 or K[PtCl3(C2H4)](H2O) gave (Phebox)MIICl complexes (4, M = Pd; 5, M = Pt) in modest to good yields. The (Phebox)PtIvCl3 complexes 8 were also synthesized by the reaction of 5 with CuCl2(H2O)2 as an oxidant. These chloride complexes, 4, 5, and 8, were in turn converted to the cationic complexes by treatment with the corresponding silver salts (AgX: X = BF4, OTf, OCOCF3). X-ray structure studies revealed that the octahedral structure of (Phebox)PtIVCl2 fragment G is isosteric with the (Phebox)RhIIICl2 fragment D, and the (Phebox)MII fragment H (M = Pd, Pt) is almost the same configuration with a square-planar structure. In these complexes, the cationic BF4 aqua complexes (9, M = PdII; 10, M = PtII; 11, M = PtIv) were found to act as chiral catalysts for the aldol-type condensation of isocyanides and aldehydes in the presence of i-Pr2NEt. Excellent trans diastereoselectivities and modest to good enantioselectivities were obtained in the reaction of tosylmethyl isocyanide (TosMIC, 1) by the use of [(i-Pr-Phebox)PtII(H2O)](BF4) (i-Pr-10).
- Motoyama, Yukihiro,Kawakami, Hidekazu,Shimozono, Kayoko,Aoki, Katsuyuki,Nishiyama, Hisao
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- Comparison of extended x-ray absorption fine structure and Scherrer analysis of x-ray diffraction as methods for determining mean sizes of polydisperse nanoparticles
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Curve fitting of extended x-ray absorption fine structure (EXAFS) spectra, transmission electron microscopy (TEM) imaging, and Scherrer analysis of x-ray diffraction (XRD) are compared as methods for determining the mean crystallite size in polydisperse s
- Calvin,Luo,Caragianis-Broadbridge,McGuinness,Anderson,Lehman,Wee,Morrison,Kurihara
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- A new stacking variant of Na2Pt(OH)6
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A new stacking variant of sodium hexa-hydroxo platinate(IV), Na2Pt(OH)6, was synthesized and its structure elucidated through X-ray diffraction. The new polymorph was prepared by direct reaction of PtO2 with an excess of NaOH solution applying elevated oxygen pressure at 300°C. The structure consists of layers of edge sharing Pt(OH)6 and Na(OH)6 octahedra. These layers are separated by an edge-to-edge distance of ~2.4 ?. The packing of the hydroxide ions corresponds to the hcp sequence, the title compound thus may be regarded a cation ordered variant of the Brucite structure type. During heating above T~300°C all constitutional water is released, and anhydrous Na2PtO3 remains as the solid residue.
- Thakur, Gohil S.,Reuter, Hans,Felser, Claudia,Jansen, Martin
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- X-ray structure and multinuclear NMR studies of platinum(II) complexes with 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one
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New dichloride platinum(II) complexes with 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) have been synthesized and characterized by thermal analysis, infrared and 1H, 13C, 15N, 195Pt NMR spectroscopy. X-ray crystal structures of cis-PtCl2(NH3)(HmtpO) (1) and cis-PtCl2(HmtpO)2 · 4H2O (2b) were determined to R = 0.0332 and R = 0.0802, respectively. In both complexes the Pt(II) ions have a square-planar geometry with two adjacent corners being occupied by two nitrogens of HmtpO molecules for 2b or NH3 and HmtpO molecules for 1, whereas the remaining adjacent corners are occupied by two chloride anions. Spectroscopic data confirm the square planar geometry with N(3) bonded HmtpO, S-bonded dimethylsulfoxide and two trans chloride anions for trans-PtCl2(dmso) · 4H2O (3).
- ?akomska, Iwona,Wojtczak, Andrzej,Sitkowski, Jerzy,Kozerski, Lech,Sz?yk, Edward
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- Pd3Fe and Pt monolayer-modified Pd3Fe electrocatalysts for oxygen reduction
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In a search for electrocatalysts based on other metals with comparable attributes to very scarce and expensive Pt, we studied the kinetics of the oxygen reduction reaction (ORR) on carbon-supported Pd3Fe alloy nanoparticles in HClO4 and NaOH solutions. In acid solution, the electrocatalyst's activity for the ORR is slightly higher than that of commercial Pt/C. The reaction kinetics involves predominantly a four-electron reduction with the first charge-transfer step being the rate-determining one. The synthesis of a Pd overlayer on the Pd3Fe alloy's surface at elevated temperatures is due to strong segregation effects. The major cause of this electrocatalyst's high activity appears to be the downshifting of the d-band center of Pd overlayer, resulting in a weaker interaction between the oxygen-containing species and the Pd surface. We demonstrated a further enhancement of the ORR kinetics with a Pt monolayer-covered Pd3Fe/C electrocatalyst. In HClO4 solution, the mass-specific activity of Pt/Pd3Fe/C was about five times higher than that of commercial Pt/C, surpassing the Pt/Pd/C. In situ XANES data indicate that this elevated ORR activity may be due to the decreased formation of PtOH, and weaker oxygen adsorption on Pt/Pd3Fe/C. by Oldenbourg Wissenschaftsverlag.
- Shao,Sasaki,Liu,Adzic
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- Vapor-deposited Pt and Pd-Pt catalysts for solid acid fuel cells: Short range structure and interactions with the CsH2PO4 electrolyte
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State-of-the-art cathodes for solid acid fuel cells (SAFCs) based on the crystalline electrolyte CsH2PO4 (CDP) are comprised of a proton-conducting CDP network coated by a vapor-deposited nanostructured catalyst. Pd-rich (85 at%Pd) Pt-Pd oxygen reduction catalysts vapor-deposited on CDP display both extraordinary activity for oxygen reduction and poor stability in cathodes for SAFCs operating at 250 °C. Similar catalysts with lower Pd content (57 at%Pd) are less active and more stable. Using X-ray absorption spectroscopy (XAS), we find that these catalysts are structurally similar and that structural variations are insufficient to explain the observed differences in activity. XAS and solid-state and solution nuclear magnetic resonance (NMR) also show that additional water-soluble chemical species are present in the Pd-rich electrode after fuel cell operation. We attribute the presence of these species to the reactivity of the Pd-rich catalyst with CsH2PO4 and suggest that these products are the cause of the observed deactivation.
- Papandrew, Alexander B.,John, Samuel St.,Elgammal, Ramez A.,Wilson, David L.,Atkinson, Robert W.,Lawton, Jamie S.,Arruda, Thomas M.,Zawodzinski, Thomas A.
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- Electro-oxidation of some phenolic compounds by electrogenerated O 3 and by direct electrolysis at PbO2 anodes
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The oxidative degradation of phenolic compounds (4-chlorophenol and 4-nitrophenol) was studied using different electrochemical systems involving ozone formation at PbO2 anodes: (i) direct electrolysis at constant current; (ii) ex-situ use of O3 and (iii) combined use of anodically generated stream of O3/O2 fed into the cathode where H2O2 is electrogenerated by O2 reduction. We show that the latter advanced oxidation method gives the best results: it is a Fenton-type degradation of the target pollutants taking place in the cathodic compartment by reason of the highly oxidizing environment brought about by radicals that are formed mainly in the reactions of O3 with OH - and HO2-.
- Amadelli, Rossano,Samiolo, Luca,Battisti, Achille De,Velichenko, Alexander B.
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- Specific features of the formation of Pt(Cu) catalysts by galvanic displacement with carbon nanowalls used as support
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Microamounts of Cu are applied by the methods of electrodeposition (Cu ed) and magnetron sputtering (Cuspr) on a new carbon material, carbon nanowalls (CNW). The galvanic displacement (GD) of Cu ed and Cuspr in a PtCl42- solution (with 0.5 M H2SO4 as the supporting electrolyte) produces Pt(Cu)/CNW catalysts. The possibility of using open-circuit potential transients recorded in the course of GD for monitoring the surface layer composition is considered. The stable Pt(Cu)st samples are characterized by several methods (SEM, TEM, XPS, voltammetry, etc.). It is shown that Pt(Cu)st has structure of the core(Pt, Cu)-shell(Pt) type with the average atomic ratio Pt:Cu (%) ～ 57:43 for Cued and ～80:20 for Cuspr. The formation of the dense Pt shell is also confirmed by the data on the electrocatalytic activity of synthesized samples in the methanol oxidation reaction. The reasons for deviations in the properties of Pt(Cu) st/CNW samples formed from Cued and Cuspr are discussed. The high specific surfaces of the Pt(Cu)st/CNW catalyst obtained from Cued (>40 m2/g Pt) with the simultaneous decrease in the Pt content makes this material promising for using in the platinum-catalyzed processes (particularly, in fuel cells).
- Podlovchenko,Krivchenko,Maksimov,Gladysheva,Yashina,Evlashin,Pilevsky
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- Scanning tunneling microscopy study of platinum deposited on graphite by metalorganic chemical vapor deposition
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The growth of thin Pt(111) films on highly oriented pyrolytic graphite (HOPG) by metalorganic chemical vapor deposition has been followed by scanning tunneling microscopy. Depositions were carried out on substrates held at 205°C and contacted with intersecting streams of H2 and of He saturated with (η5-C5H4CH3)Pt(CH3)3. The deposition was monitored by the appearance of methane in the product stream. Deposition initiated almost immediately, in contrast with earlier studies showing a significant induction period for deposition on glass. The deposits obtained after several minutes at 205°C consisted of Pt clusters with diameters ranging from 8 to 80 angstrom along with some very much larger Pt islands. The deposits were morphologically very rough with rather well defined facet orientation. The step heights of the terraces ranged from 20 to 54 angstrom. Oval shaped disks free of apparent dislocations were also observed. One of the larger crystallites investigated was 2074 × 1482 angstrom2 and 200 angstrom in height. The deposits were non-uniform throughout the deposition. The initial crystal growth under CVD was by island nucleation, followed by a growth mode that produced a random rough surface after the islands coalesced. At early stages the films are preferentially oriented with (111) crystallites parallel to the HOPG basal plane; further growth, however, leads to a poly-crystalline deposit.
- Ngo,Brandt,Williams,Kaesz
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- New bioactive Pt(II) binary and ternary metal complexes with guaifenesin drug: Synthesis, geometrical structure, and spectroscopic and thermal characterization
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Three new binary and ternary metal complexes of Pt(II) with guaifenesin (GFS) drug have been prepared by chelation to guaifenesin ligand (as primary ligand) and glycine amino acid (HGly) and 1,10-phenanthroline (1,10-Phen) (as secondary ligands). Characterization was conducted based on elemental analysis, molar conductance, infrared (IR) spectroscopy, thermogravimetric analysis and X-ray diffraction. The complexes were found to have the formulae [Pt(GFS)2]?3H2O (1), [Pt(GFS)2(Gly)]Cl?H2O (2) and [Pt(GFS)2(Phen)]Cl2 (3). Magnetic and spectroscopic data revealed complexes 1–3 to have octahedral geometry. IR spectra suggested that GFS ligand coordinated in mononegative tridentate mode (OOO) for 1 but in neutral bidentate mode (OO) for 2 and 3. In addition, HGly behaves as mononegative bidentate coordinated to Pt(II) metal via deprotonated carboxylate O and amino group. IR data also evidenced the bidentate nature of 1,10-Phen ligand. The molecular and electronic structure of Pt(II) complex 1 was optimized theoretically and the quantum chemical parameters were calculated. Complexes 1–3 were screened for their antibacterial activity on Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Neisseria gonorrhoeae) and for their in vitro antifungal activity against Candida albicans. The three Pt(II) complexes showed remarkable biological and cytotoxic activity. The chelates were also screened for their in vitro anticancer activity against the MFC7 breast cell line. Complex 3 showed the highest activity with a low IC50 value of 3.38?μg?ml?1.
- Mahmoud, Walaa H.,Mohamed, Gehad G.,Mahmoud, Nessma F.
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- Preferential CO oxidation promoted by the presence of H2 over K-Pt/Al2O3
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In preferential CO oxidation in H2-rich gas, K-Pt/Al 2O3 (K/Pt =10) was very effective in decreasing CO concentration below 10 ppm in the 375-410 K range, and the turnover frequency of the K-Pt/Al2O3
- Minemura, Yuji,Ito, Shin-Ichi,Miyao, Toshihiro,Naito, Shuichi,Tomishige, Keiichi,Kunimori, Kimio
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- Electrochemical deposition of platinum on fluorine-doped tin oxide: The nucleation mechanisms
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We report the electrochemical formation of Pt particles on fluorine-doped tin oxide electrodes by varying the concentration of PtCl4 2- ions and the overpotentials within the mass-transfer-limited region. The nucleation mechanisms ar
- Ko, Young-Seon,Kwon, Young-Uk
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- One-pot synthesis of PtSn bimetallic composites and their application as highly active catalysts for ethanol electrooxidation
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PtSn nanoparticles with different molar ratio are fabricated by chemical reduction to form a relatively efficient catalyst for ethanol electrooxidation in an alkaline solution of KOH (1.0 m) containing C2H5OH (1.0 m). The surface composition and structure of the as-prepared catalysts are characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray spectroscopy (EDX). Cyclic voltammogram (CV) and chronoamperometric (CA) measurements are used to evaluate the electrochemical activity and stability of the as-prepared catalysts. As the content of Sn in the catalysts changed, the catalysts showed different catalytic activity. The results indicate that the moderate addition of Sn can enhance the catalytic activity of Pt catalyst, and Pt3Sn1 displays the highest catalytic activity and stability among the as-synthesized PtSn nanoparticles during the electrooxidation of ethanol. Bimetallic PtSn electrocatalysts with different atomic ratios have been fabricated by a chemical reduction in a facile manner. Electrochemical measurements reveal that Pt3Sn1 catalysts exhibit the highest efficiency and stable electrocatalytic performance towards ethanol electrooxidation in an alkaline medium (see figure).
- Feng, Yue,Wang, Caiqin,Bin, Duan,Zhai, Chunyang,Ren, Fangfang,Yang, Ping,Du, Yukou
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- Catalyst Architecture for Stable Single Atom Dispersion Enables Site-Specific Spectroscopic and Reactivity Measurements of CO Adsorbed to Pt Atoms, Oxidized Pt Clusters, and Metallic Pt Clusters on TiO2
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Oxide-supported precious metal nanoparticles are widely used industrial catalysts. Due to expense and rarity, developing synthetic protocols that reduce precious metal nanoparticle size and stabilize dispersed species is essential. Supported atomically dispersed, single precious metal atoms represent the most efficient metal utilization geometry, although debate regarding the catalytic activity of supported single precious atom species has arisen from difficulty in synthesizing homogeneous and stable single atom dispersions, and a lack of site-specific characterization approaches. We propose a catalyst architecture and characterization approach to overcome these limitations, by depositing ～1 precious metal atom per support particle and characterizing structures by correlating scanning transmission electron microscopy imaging and CO probe molecule infrared spectroscopy. This is demonstrated for Pt supported on anatase TiO2. In these structures, isolated Pt atoms, Ptiso, remain stable through various conditions, and spectroscopic evidence suggests Ptiso species exist in homogeneous local environments. Comparing Ptiso to ～1 nm preoxidized (Ptox) and prereduced (Ptmetal) Pt clusters on TiO2, we identify unique spectroscopic signatures of CO bound to each site and find CO adsorption energy is ordered: Ptiso ≥ Ptmetal ox. Ptiso species exhibited a 2-fold greater turnover frequency for CO oxidation than 1 nm Ptmetal clusters but share an identical reaction mechanism. We propose the active catalytic sites are cationic interfacial Pt atoms bonded to TiO2 and that Ptiso exhibits optimal reactivity because every atom is exposed for catalysis and forms an interfacial site with TiO2. This approach should be generally useful for studying the behavior of supported precious metal atoms.
- DeRita, Leo,Dai, Sheng,Lopez-Zepeda, Kimberly,Pham, Nicholas,Graham, George W.,Pan, Xiaoqing,Christopher, Phillip
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- Catalytic oxidation of carbon monoxide over radiolytically prepared Pt nanoparticles supported on glass
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Platinum nanoparticles have been prepared by radiolytic and chemical methods in the presence of stabilizer gelatin and SiO2 nanoparticles. The formation of Pt nanoparticles was confirmed using UV-vis absorption spectroscopy and transmission electron microscopy (TEM). The prepared particles were coated on the inner walls of the tubular pyrex reactor and tested for their catalytic activity for oxidation of CO. It was observed that Pt nanoparticles prepared in the presence of a stabilizer (gelatin) showed a higher tendency to adhere to the inner walls of the pyrex reactor as compared to that prepared in the presence of silica nanoparticles. The catalyst was found to be active at ≥150 °C giving CO2. Chemically reduced Pt nanoparticles stabilized on silica nanoparticles gave ～7% CO conversion per hour. However, radiolytically prepared Pt nanoparticles stabilized by gelatin gave ～10% conversion per hour. Catalytic activity of radiolytically prepared platinum catalyst, coated on the inner walls of the reactor, was evaluated as a function of CO concentration and reaction temperature. The rate of reaction increased with increase in reaction temperature and the activation energy for the reaction was found to be ～108.8 kJ mol-1. The rate of CO2 formation was almost constant (～1.5 × 10-4 mol dm -3 h-1) at constant O2 concentration (6.5 × 10-3 mol dm-3) with increase in CO concentration from 2 × 10-4 mol dm-3 to 3.25 × 10 -3 mol dm-3. The data indicate that catalytic oxidation of CO takes place by Eley-Rideal mechanism.
- Kapoor,Belapurkar,Mittal,Mukherjee
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- Pt, PtNi and PtCoNi film electrocatalysts prepared by chemical vapor deposition for the oxygen reduction reaction in 0.5 M KOH
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Pt, PtNi and PtCoNi films were deposited by metal-organic chemical vapor deposition (MOCVD) upon glassy carbon rods. Physical characterization was performed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. It was found that films consisted of crystalline and nanometric particles with more than one phase as a result of the interactions among reactants, intermediate and product species during the chemical vapor deposition process. The electrochemical set-up to test the films for the oxygen reduction reaction was a three-electrode cell where the reference electrode was Hg/HgO/0.5 M KOH, the working electrodes were the films upon glassy carbon rods. The films were tested in 0.5 M KOH electrolyte; polarization curves were obtained by using the rotating disk electrode technique to evaluate the electrocatalytic activity of the prepared films. The kinetic parameters of Pt, PtNi and PtCoNi electrocatalysts were calculated. PtCoNi showed the best performance for the oxygen reduction reaction due to a synergetic effect of alloying Pt with transition metals.
- García-Contreras,Fernández-Valverde,Vargas-García
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- Asymmetrically strained hcp rhodium sublattice stabilized by 1D covalent boron chains as an efficient electrocatalyst
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Intermetallic rhodium boride (RhB) comprising an asymmetrically strained hcp Rh sublattice is synthesized. The covalent interaction of interstitial boron atoms is found to be the main contributor to the generation of asymmetric strains and the stabilization of the hcp Rh sublattice. In addition, RhB is identified as a hydrogen-evolving eletrocatalyst with Pt-like activity, because the Rh(d)-B(s,p) orbital hybridization induces an optimized electronic structure.
- Li, Zhenyu,Ai, Xuan,Chen, Hui,Liang, Xiao,Li, Xiaotian,Wang, Dong,Zou, Xiaoxin
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supporting information
p. 5075 - 5078
(2021/05/28)
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- Reactions of organoplatinum complexes with dimethylamine-borane
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The reactions of dimethylamine-borane with platinum(ii) or platinum(iv) triflate complexes gave, not the anticipated σ-complexes, but the respective hydridoplatinum complexes. The reaction with [Pt(OTf)Me3(NN)], with NN = 2,2′-bipyridine (bipy) and 4,4′-di-t-butyl-2,2′-bipyridine (bu2bipy), gave the rare stable bridging hydridoplatinum(iv) complexes [μ-H{PtMe3(NN)}2][OTf] and the reaction with [Pt(O2CCF3)Me(NN)] gave the unstable hydridoplatinum(ii) complex [PtHMe(NN)]. The unstable hydridoplatinum(ii) complexes could be trapped by reaction with methyl acrylate by forming the insertion products [PtCl(CHMeCO2Me)(bipy)] and [Pt(CHMeCO2Me)2(bipy)]. The complex [PtCl(CHMeCO2Me)(bipy)] reacted with methyl iodide to give [PtClIMe(CHMeCO2Me)(bipy)], by cis oxidative addition, and the presence of two chiral centers in the product platinum(iv) complex allowed a detailed stereochemical pathway to be proposed. This journal is
- Puddephatt, Richard J.,Robinson, Shawn
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p. 14965 - 14972
(2021/09/04)
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- New perspective of a nano-metal preparation pathway based on the hexahydro-closo-hexaborate anion
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Today, metal-based nanomaterials play an increasingly important role in the energy, environment, medical and health fields. In order to meet the needs of various fields, it is necessary to continuously develop advanced technologies for preparing metal-based materials. Inspired by previous research, the results of a proof-of-concept experiment show that the hexahydro-closo-hexaborate anion (closo-[B6H7]?) in the borane cluster family has properties similar to NaBH4.Closo-[B6H7]?can not only convert common precious metal ions such as Au3+, Pd2+, Pt4+and Ag+to the corresponding zero-valence state, but also convert some non-precious metals such as Cu2+and Ni2+to the zero-valent or oxidation state.Closo-[B6H7]?moderate reduction to cause rapid aggregation of metal-based materials is not easy compared with NaBH4. Compared withcloso-[B12H12]2?,closo-[B6H7]?achieves the conversion of Pt4+to Pt0under ambient conditions, and its reduction performance extends to non-precious metals. The excellent stability and easy modification characteristics determine the universality of thecloso-[B6H7]?reduction strategy for metal ions.
- Liu, Jun,Zhang, Haibo,Zhao, Xue
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p. 33444 - 33449
(2020/09/21)
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- Intermetallic Nanocatalysts from Heterobimetallic Group 10-14 Pyridine-2-thiolate Precursors
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Intermetallic compounds are atomically ordered inorganic materials containing two or more transition metals and main-group elements in unique crystal structures. Intermetallics based on group 10 and group 14 metals have shown enhanced activity, selectivity, and durability in comparison to simple metals and alloys in many catalytic reactions. While high-temperature solid-state methods to prepare intermetallic compounds exist, softer synthetic methods can provide key advantages, such as enabling the preparation of metastable phases or of smaller particles with increased surface areas for catalysis. Here, we study a generalized family of heterobimetallic precursors to binary intermetallics, each containing a group 10 metal and a group 14 tetrel bonded together and supported by pincer-like pyridine-2-thiolate ligands. Upon thermal decomposition, these heterobimetallic complexes form 10-14 binary intermetallic nanocrystals. Experiments and density functional theory (DFT) computations help in better understanding the reactivity of these precursors toward the synthesis of specific intermetallic binary phases. Using Pd2Sn as an example, we demonstrate that nanoparticles made in this way can act as uniquely selective catalysts for the reduction of nitroarenes to azoxyarenes, which highlights the utility of the intermetallics made by our method. Employing heterobimetallic pincer complexes as precursors toward binary nanocrystals and other metal-rich intermetallics provides opportunities to explore the fundamental chemistry and applications of these materials.
- Adamson, Marquix A. S.,Chen, Yunhua,Daniels, Carena L.,Dorn, Rick W.,Fan, Huajun,Knobeloch, Megan,Rossini, Aaron J.,Vela, Javier,Wu, Hao,Yox, Philip,Zhou, Guoquan
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supporting information
(2020/03/13)
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- Synthesis, physico-chemical characterization and bioevaluation of Ni(II), Pd(II), and Pt(II) complexes with 1-(o-tolyl)biguanide: Antimicrobial and antitumor studies
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New complexes of type [M(tbg)2]Cl2 [tbg = 1-(o-tolyl)biguanide; M = Ni(II), Pd(II), and Pt(II)] were synthesized and characterized to develop new biologically active compounds. The features of the complexes were assigned from microanalytical and thermal data. The NMR, FT-IR, and UV-Vis spectra were established by comparison with HtbgCl. All complexes exhibit a square-planar geometry resulting from the chelating behavior of tbg. The HtbgCl and [Ni(tbg)2]Cl2 complexes were fully characterized by single-crystal X-ray diffraction. The HtbgCl species crystallize in the monoclinic C2/c spatial group, while the Ni(II) complex adopts an orthorhombic Pna21 spatial group. The structure is stabilized by a complex hydrogen bonds network. The in vitro antimicrobial assays revealed improved antimicrobial activity for complexes in comparison with the ligand against both planktonic and biofilm embedded microbial cells. The most efficient compound, showing the largest spectrum of antimicrobial activity, including Gram-positive and Gram-negative bacteria, as well as fungal strains, in both planktonic and biofilm growth states was the Pd(II) complex, followed by the Pt(II) complex. The Pt(II) compound exhibited the most significant antiproliferative activity on the human cervical cancer SiHa cell line, inducing a cell cycle arrest in the G2/M phase.
- Nu??, Ileana,Badea, Mihaela,Chifiriuc, Mariana Carmen,Bleotu, Coralia,Popa, Marcela,Daniliuc, Constantin-Gabriel,Olar, Rodica
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- Solid-Phase Reaction of Tetraammineplatinum(II) Chloride with Ammonium Heptamolybdate
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Abstract: The solid-phase reaction of [Pt(NH3)4]Cl2 and (NH4)6Mo7O24 under argon in the temperature range from 50 to 500°C was studied by thermal analysis and mass spectrometry.
- Buslaeva, T. M.,Fesik, E. V.,Melnikova, T. I.,Tarasova, L. S.
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p. 1020 - 1024
(2020/07/27)
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- Reaction of [Pt(NH3)4]Cl2 with NH4VO3 in an Alkaline Solution at 190°C in Autoclave
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Abstract: The reaction of[Pt(NH3)4]Cl2with NH4VO3 in alkaline solutionin an autoclave at 190°C was studied. The solid autoclave thermolysis productwas characterized by the methods of X-ray phase analysis, scanning electronmicroscopy, energy-dispersive X-ray spectroscopy, dynamic light scattering, andelemental analysis. The product is represented by two phases: Pt and aPt3V solid solution in the form of two types ofparticles of different morphology with a size less than 1 μm. The reactionstoichiometry{9[Pt(NH3)4]Cl2,18NH4VO3, 18KOH} correspondsto the found amount of free ammonia (14NH3) formed underthe selected conditions.
- Arkhipushkin, I. A.,Buslaeva, T. M.,Fesik, E. V.
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p. 2147 - 2151
(2020/12/25)
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- Process for the Pt(II) synthesis of metal complexes, Pt(II) the complexes thereof, and the use of such complexes which can be optically activated in the hydrogenation of hydrogenated silicon
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A method of synthesising a Pt(ll) complex includes a first step of preparing a reaction mixture comprising a water-soluble hexachloroplatinate salt and a compound according to Formula I', or salt thereof, and allowing the water-soluble hexachloroplatinate salt and the compound according to Formula I' to react and a second step of adding a further quantity of the compound according to Formula I', or a salt thereof, to the reaction mixture. Products of this method are Pt(ll) complexes according to Formula I The Pt(ll) complexes are useful as catalysts in hydrosilylation reactions.
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Paragraph 0256-0257
(2020/04/16)
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- Calcination Atmosphere Regulated Morphology and Catalytic Performance of Pt/SiO2 in Gas-phase Oxidative Dehydrogenation of KA-oil
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It is industrially attractive to produce cyclohexanone directly from gas-phase oxidative dehydrogenation (ODH) of KA-oil (a mixture of cyclohexanone and cyclohexanol) since extra alcohol-ketone separation process can be potentially omitted. Herein, by simply tuning the calcination atmosphere of Pt/SiO2, we successfully regulated the morphology of Pt nanoparticles and optimized their catalytic performance in ODH of KA-oil. Pt/SiO2 calcined in O2 atmosphere showed a cube-like morphology and achieved a 78.1 % cyclohexanone yield at 170 °C, which surpassed its counterpart calcined in H2 and most of the reported catalysts. Further experimental and theoretical calculation results indicated that cubic Pt nanoparticles possessed stronger adsorption ability to cyclohexanol and therefore performed better in ODH of KA-oil.
- Hong, Wei,Wang, Zhi-Qiang,Zou, Shihui,Zhou, Yuheng,Lu, Linfang,Zhou, Qiuyue,Gong, Xue-Qing,Fan, Jie
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p. 5689 - 5697
(2018/12/11)
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- Ice Melting to Release Reactants in Solution Syntheses
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Aqueous solution syntheses are mostly based on mixing two solutions with different reactants. It is shown that freezing one solution and melting it in another solution provides a new interesting strategy to mix chemicals and to significantly change the reaction kinetics and thermodynamics. For example, a precursor solution containing a certain concentration of AgNO3 was frozen and dropped into a reductive NaBH4 solution at about 0 °C. The ultra-slow release of reactants was successfully achieved. An ice-melting process can be used to synthesize atomically dispersed metals, including cobalt, nickel, copper, rhodium, ruthenium, palladium, silver, osmium, iridium, platinum, and gold, which can be easily extended to other solution syntheses (such as precipitation, hydrolysis, and displacement reactions) and provide a generalized method to redesign the interphase reaction kinetics and ion diffusion in wet chemistry.
- Wei, Hehe,Huang, Kai,Zhang, Le,Ge, Binghui,Wang, Dong,Lang, Jialiang,Ma, Jingyuan,Wang, Da,Zhang, Shuai,Li, Qunyang,Zhang, Ruoyu,Hussain, Naveed,Lei, Ming,Liu, Li-Min,Wu, Hui
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supporting information
p. 3354 - 3359
(2018/02/21)
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- Complex salts of Pd(ii) and Pt(ii) with Co(ii) and Ni(ii) aqua-cations as single-source precursors for bimetallic nanoalloys and mixed oxides
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A series of highly soluble double complex salts [M′(H2O)6][M′′(NO2)4]·2H2O (M′ = Ni, Co; M′′ = Pd, Pt) have been synthesized, studied and used as single-source precursors for bimetallic nanoalloys and metal-oxide composites. According to the results of simultaneous thermal analysis-mass spectrometry (STA-MS), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), thermolysis of the compounds in diverse atmospheres (O2, He, and H2), delafossite-type mixed oxides M′′CoO2/(NiO + M′′O), metal-oxide composition M′O + M′′ and bimetallic solid solution M′0.5M′′0.5, respectively. In an H2 atmosphere an instant isolation of the equiatomic solid solution occurs at lower than 200 °C with simultaneous reduction of noble and ignoble metals. The bimetallic products can be superstructurally ordered at higher temperatures. The solubility of precursors in organic solvents allows carrying out an impregnation of the salts inside multiwalled carbon nanotubes; subsequent heating in H2 yields intercalated nanoparticles of ～2-4 nm in size.
- Zadesenets, Andrey V.,Filatov, Evgeniy Yu.,Plyusnin, Pavel E.,Asanova, Tatyana I.,Korolkov, Ilya V.,Baidina, Iraida A.,Shlyakhova, Elena V.,Asanov, Igor P.,Korenev, Sergey V.
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p. 8843 - 8850
(2018/06/08)
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- Synthesis, spectroscopic, thermal, antimicrobial and electrochemical characterization of some novel Ru(iii), Pt(iv) and Ir(iii) complexes of pipemidic acid
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Three new solid complexes of pipemidic acid (Pip-H) with Ru3+, Pt4+ and Ir3+ were synthesized and characterized. Pipemidic acid acts as a uni-dentate chelator through the nitrogen atom of the -NH piperazyl ring. The spectroscopic data revealed that the general formulas of Pip-H complexes are [M(L)n(Cl)x]·yH2O ((1) M = Ru3+, L: Pip-H, n = 3, x = 3, y = 6; (2) M = Pt4+, L: Pip-NH4, n = 2, x = 4, y = 0 and (3) M = Ir3+, L: Pip-H, n = 3, x = 3, y = 6). The number of water molecules with their locations inside or outside the coordination sphere were assigned via thermal analyses (TG, DTG). The DTG curves refer to 2-3 thermal decomposition steps where the first decomposition step at a lower temperature corresponds to the loss of uncoordinated water molecules followed by the decomposition of Pip-H molecules at higher temperatures. Thermodynamic parameters (E?, ΔS?, ΔH? and ΔG?) were calculated from the TG curves using Coats-Redfern and Horowitz-Metzeger non-isothermal models. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques were carefully used to assign properly the particle sizes of the prepared Pip-H complexes. The biological enhancement of Pip-H complexes rather than free chelate were assessed in vitro against four kinds of bacteria G(+) (Staphylococcus epidermidis and Staphylococcus aureus) and G(-) (Klebsiella and Escherichia coli) as well as against the human breast cancer (MCF-7) tumor cell line.
- Alibrahim, Khuloud A.,Al-Saif, Foziah A.,Alghamdi,El-Shahawi,Moustafa,Refat, Moamen S.
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p. 22515 - 22529
(2018/07/05)
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- A gigantic polyoxozirconate with visible photoactivity
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We present a gigantic polyoxozirconate nanocluster (Zr18O21(μ2-OH)2(OOCPh)28), involving 6, 7 and 8-coordinated Zr atoms. It exhibits visible light driven photocatalytic activity for H2 evolution. The current results could represent a prelude of polyoxozirconate-based photocatalysis.
- Xu, Tingting,Hou, Xudong,Wang, Yang,Zhang, Jun,Zhang, Junxiang,Liu, Bo
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supporting information
p. 10185 - 10188
(2017/08/15)
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- Isolation of homoleptic platinum oxyanionic complexes with doubly protonated diazacrown cation
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Doubly protonated diazacrown ether cation (1,4,10,13-tetraoxa-7,16-diazoniacyclooctadecane DCH22+) was used for the efficient isolation of the homoleptic platinum complexes [Pt(NO3)6]2- and [Pt(C
- Vasilchenko, Danila,Tkachev, Sergey,Baidina, Iraida,Romanenko, Galina,Korenev, Sergey
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p. 855 - 859
(2016/12/16)
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- PtPb/PtNi Intermetallic Core/Atomic Layer Shell Octahedra for Efficient Oxygen Reduction Electrocatalysis
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Although explosive studies on pursuing high-performance Pt-based nanomaterials for fuel cell reactions have been carried out, the combined controls of surface composition, exposed facet, and interior structure of the catalyst remains a formidable challenge. We demonstrate herein a facile chemical approach to realize a new class of intermetallic Pt-Pb-Ni octahedra for the first time. Those nanostructures with unique intermetallic core, active surface composition, and the exposed facet enhance oxygen reduction electrocatalysis with the optimized PtPb1.12Ni0.14 octahedra exhibiting superior specific and mass activities (5.16 mA/cm2 and 1.92 A/mgPt) for oxygen reduction reaction (ORR) that are ～20 and ～11 times higher than the commercial Pt/C, respectively. Moreover, the PtPb1.12Ni0.14 octahedra can endure at least 15 000 cycles with negligible activity decay, showing a new class of Pt-based electrocatalysts with enhanced performance for fuel cells and beyond.
- Bu, Lingzheng,Shao, Qi,Bin,Guo, Jun,Yao, Jianlin,Huang, Xiaoqing
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p. 9576 - 9582
(2017/07/24)
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- Transition Metal-Based Thiometallates as Surface Ligands for Functionalization of All-Inorganic Nanocrystals
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We report a new family of inorganic ligands, namely, transition metal-based thiometallates, for the surface functionalization of colloidal nanocrystals (NCs). We synthesized Pt-, Fe-, Co-, and Ni-based thiometallates, in which transition metal ions were complexed with polysulfides. These inorganic anions easily exchanged the surface organic ligands of various nanocrystals of metal, semiconductor, and oxide materials, without affecting the NCs' primary structural and optical characteristics. Furthermore, upon heating, these complexes were decomposed and transformed into crystalline phases of metal sulfides or pure metals, accompanied by the evaporation of S. Based on this effect, we selectively synthesized homogeneously distributed atomic Pt clusters or Pt nanoparticles on Fe3O4 nanomaterials by heating thioplatinate-capped Fe3O4 NCs. As a model application, we tested the prepared Pt-functionalized Fe3O4 nanomaterial as a heterogeneous catalyst for CO oxidation reaction and Pt-Fe3O4 catalysts exhibited the high turnover frequency due to the homogeneous distribution of atomic Pt over Fe3O4 and the corresponding strong metal-support interaction. This approach opens up a new avenue to functionalize nanocrystals for catalytic applications.
- Jeong, Hyewon,Yoon, Sinmyung,Kim, Jung Hwa,Kwak, Do-Hyun,Gu, Da Hwi,Heo, Seung Hwae,Kim, Hyunhong,Park, Sangmin,Ban, Hyeong Woo,Park, Jongnam,Lee, Zonghoon,Lee, Jong-Soo,An, Kwangjin,Son, Jae Sung
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p. 10510 - 10517
(2018/01/10)
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- Salt-Free Reduction of Nonprecious Transition-Metal Compounds: Generation of Amorphous Ni Nanoparticles for Catalytic C-C Bond Formation
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A salt-free procedure for the generation of a wide variety of metal(0) particles, including Fe, Co, Ni, and Cu, was achieved using 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (1), which reduced the corresponding metal precursors under mild conditions. Notably, Ni particles formed in situ from the treatment of Ni(acac)2 (acac=acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C-C bond-forming reactions of aryl halides in the presence of excess amounts of 1. By examination of high-magnification transmission electron microscopy images and electron diffraction patterns, we concluded that amorphous Ni nanoparticles (Ni aNPs) were essential for the high catalytic activity.
- Yurino, Taiga,Ueda, Yohei,Shimizu, Yoshiki,Tanaka, Shinji,Nishiyama, Haruka,Tsurugi, Hayato,Sato, Kazuhiko,Mashima, Kazushi
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supporting information
p. 14437 - 14441
(2016/01/25)
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- A PROCESS FOR REDUCING CHLORONITROBENZENE CATALYZED BY PLATINUM-NANOPARTICLES STABILIZED ON MODIFIED MONTMORILLONITE CLAY
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Pto-nanoparticles of in the size range 0 - 10 nm were prepared in-situ by impregnation of H2PtCl6.6H2O into the nanopores of modified montmorillonite followed by reduction with different reducing agents like ethylene glycol, sodium citrate, hydrogen, hydrazine and sodium borohydrate. The montmorillonite was modified by activation with mineral acids under controlled condition for generating desired nanopores. XRD pattern of Pto-nanoparticles revealed the formation of face centered cubic (fcc) lattice. These supported Pto-nanoparticles show efficient catalytic activity for the selective reduction of chloronitrobenzenes. As a typical example, at a H2 pressure of 10 bars, temperature 45 °C for a period of 15 min, the Pto-nanoparticles (prepared by reduction with hydrazine) exhibit conversion of o-chloronitrobenzene upto 100 % and selectivity > 99 % to o-chloroanilines with very negligible amount of C-Cl bond cleavage.
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-
Page/Page column 13; 14
(2015/02/19)
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- Amorphous PtNiP particle networks of different particle sizes for the electro-oxidation of hydrazine
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The design of alloy networks is an important fundamental and applied research challenge in the area of catalysis due to the high surface area, gas permeability and electrical conductivity of alloy network structures. Herein amorphous PtNiP particle networks were prepared via the NaBH4 co-reduction process. Moreover, the reaction temperature control from 0 °C to 80 °C was shown to be a powerful tool for the 'tuning' of particle sizes. Electron microscopy, X-ray diffraction and selected area electron diffraction were used to show the morphology, the amorphous behavior and the changes in particle size of the particle networks. The results of the electrochemical performance showed that the amorphous PtNiP particle networks had better catalytic activity towards hydrazine oxidation compared to the Pt and PtNi networks. The electrocatalytic activity reached a peak value, 0.62 mA at -0.63 V, at a PtNiP-50 electrode. The correlation between the particle size of the amorphous PtNiP particle networks and their electrocatalytic activity for the hydrazine oxidation reaction provided the opportunity to develop highly active electrocatalysts for hydrazine fuel cells.
- Ma, Yuanyuan,Wang, Hui,Lv, Weizhong,Ji, Shan,Pollet, Bruno G.,Li, Shunxi,Wang, Rongfang
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p. 68655 - 68661
(2015/09/01)
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- Parahydrogen-induced polarization (PHIP) in heterogeneous hydrogenation over bulk metals and metal oxides
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The results show that, in general, observation of PHIP effects on metals does not require the presence of a support. In addition, certain metal oxides can produce PHIP effects in the absence of a supported metal. The new promising catalysts for producing PHIP heterogeneously have been identified. The Royal Society of Chemistry.
- Kovtunov, Kirill V.,Barskiy, Danila A.,Salnikov, Oleg G.,Khudorozhkov, Alexander K.,Bukhtiyarov, Valery I.,Prosvirin, Igor P.,Koptyug, Igor V.
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supporting information
p. 875 - 878
(2014/01/06)
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- FePt nanoalloys anchored reduced graphene oxide as high-performance electrocatalysts for formic acid and methanol oxidation
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Reduced graphene oxide (RGO) supported FePt alloy nanoparticles are synthesized as high-performance electrocatalysts for methanol and formic acid (FA) oxidation. The microstructure, composition and morphology of the sample are systematically characterized
- Guo, Jinxue,Sun, Yanfang,Zhang, Xiao,Tang, Lin,Liu, Hongtian
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p. 286 - 291
(2014/05/06)
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- FeSe2 films with controllable morphologies as efficient counter electrodes for dye-sensitized solar cells
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The FeSe2 films with controllable morphologies (including 3D flower-like and sphere-shaped) have been applied as the counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). It is found that 3D flower-like FeSe2 CEs perform c
- Wang, Wenjun,Pan, Xu,Liu, Weiqing,Zhang, Bing,Chen, Haiwei,Fang, Xiaqin,Yao, Jianxi,Dai, Songyuan
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supporting information
p. 2618 - 2620
(2014/03/21)
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- Pulse reverse electrodeposition of Pt-Co alloys onto carbon cloth electrodes
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Galvanostatic pulse reverse (PR) electrodeposition of Pt-Co alloys onto pretreated carbon cloth from sulfate solutions has been conducted. The aim is to utilize the anodic current applied during the reverse time to manipulate the morphology and composition of the Pt-Co alloys through a dealloying process. The cathodic current density was found to have a strong effect on the amount and the morphology of the deposited Pt-Co, but not on its composition, over the tested range (20-200 mA cm-2). A higher current density enhances the Pt-Co nucleation process leading to smaller and finer grained Pt-Co alloy electrodeposits, and ultimately to a higher electroactive surface area. Applying the anodic current over a current density range of 50-200 mA cm-2 does not substantially alter the amount, morphology or composition of the deposited Pt-Co alloys, with the Pt contents remaining between 91 and 94 mol%. For the PR electrodeposition under the conditions studied, regardless of the magnitude applied, the anodic current does not indicate any dissolution of the Pt-Co alloy deposits, which is supported by the anodic dissolution experiment. Thus, the morphology and composition of the Pt-Co alloy deposits produced by PR electrodeposition are not significantly different from those produced by pulse current electrodeposition at the same cathodic current density.
- Chaisubanan, Napapat,Tantavichet, Nisit
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- Probing chemistry and kinetics of reactions in heterogeneous catalysts
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Using benzene hydrogenation over Pt/SiO2 as an industrially-relevant example, we show that state-of-the-art neutron total scattering methods spanning a wide Q-range now permit relevant time-resolved catalytic chemistry to be probed directly in situ within the pore of the catalyst. The method gives access to the reaction rates on both nanometric and atomic length scales, whilst simultaneously providing an atomistic structural viewpoint on the reaction mechanism itself.
- Youngs, Tristan G. A.,Manyar, Haresh,Bowron, Daniel T.,Gladden, Lynn F.,Hardacre, Christopher
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p. 3484 - 3489
(2013/11/19)
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- Hierarchical assemblies of CdxZn1-xS complex architectures and their enhanced visible-light photocatalytic activities for H2-production
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The shape-controlled synthesis of hierarchically micro- and nanostructured materials has opened up new opportunities to improve their properties. In this work, CdxZn1xS complex architectures, such as microflowers and microspheres, were prepared through a facile solvothermal method, by using diethylenetriamine (DETA) and water as solvent. Within the Zn content increase from 0.2 to 0.8 in the CdxZn1 xS solid solution, the morphology transformed progressively from microflowers agglomerates to microspheres. The photocatalytic H2 evolution over the solid solutions was further investigated through the H 2 evolution from aqueous solutions containing S2-/SO 2-3, and the highest H2 evolution rate without co-catalysts even reached 1.8 mmol g1 h1. The reasons for the difference in the photocatalytic properties of these CdxZn 1xS architectures were also investigated. The morphology change of CdxZn1xS solid solution leads to different BET and surface defects, finally resulting in the variation of photocatalytic activity.
- Wang, Jian,Li, Bo,Chen, Jiazang,Li, Li,Zhao, Jianghong,Zhu, Zhenping
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p. 571 - 576
(2013/10/01)
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- B-site deficiencies in A-site-ordered perovskite LaCu3Pt 3.75O12
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An A-site-ordered perovskite LaCu3Pt3.75O 12 was synthesized by replacing Ca2+ with La3+ in a cubic quadruple AA′3B4O12-type perovskite CaCu3Pt4O12 under high-pressure and high-temperature of 15 GPa and 1100 C. In LaCu3Pt 3.75O12, 1/16 of B-site cations are vacant to achieve charge balance. The B-site deficiencies were evidenced by crystal structure refinement using synchrotron X-ray powder diffraction, hard X-ray photoemission spectroscopy, and soft X-ray absorption spectroscopy, leading to the ionic model La3+Cu2+3Pt4+3.75O 2-12. Magnetic susceptibility data for this compound indicated a spin-glass-like behavior below Tg = 3.7 K, which is attributed to disturbance of the antiferromagnetic superexchange interaction by the B-site deficiencies.
- Ochi, Mikiko,Yamada, Ikuya,Ohgushi, Kenya,Kusano, Yoshihiro,Mizumaki, Masaichiro,Takahashi, Ryoji,Yagi, Shunsuke,Nishiyama, Norimasa,Inoue, Toru,Irifune, Tetsuo
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p. 3985 - 3989
(2013/05/21)
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- Various metal nanoparticles produced by accelerated electron beam irradiation of room-temperature ionic liquid
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Various metal nanoparticles including base metal were produced by a brief accelerated electron beam irradiation of 1-alkyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide room-temperature ionic liquid without a stabilizing agent, which is usually employed so as to prevent aggregation.
- Tsuda, Tetsuya,Sakamoto, Taiki,Nishimura, Yoshitomo,Seino, Satoshi,Imanishi, Akihito,Kuwabata, Susumu
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p. 1925 - 1927
(2012/03/13)
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- Enhanced electrocatalytic performance due to anomalous compressive strain and superior electron retention properties of highly porous Pt nanoparticles
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The shape and structure of electrocatalysts at the nanoscale level have a decisive effect on their activity and durability in low-temperature fuel cells. Herein, we report the discovery of unexpected structural phenomena in exotic nanostructures: the anomalous compressive strain and superior electron retention properties of highly porous Pt (HP-Pt) nanoparticles synthesized using a weakly interacting organic capping agent, tetradecyl trimethyl ammonium bromide. Even though the particle size of the HP-Pt nanoparticles was much larger than those of commercial electrocatalysts, bond length shortening occurred anomalously, and the downshifted d-band center eventually led to increased oxygen reduction reaction activity. This is because the HP-Pt nanoparticles had a highly porous urchin-like dendritic structure, interestingly in the single-crystalline phase, despite the large particle size. In addition, their electron retention properties were superior to those of commercial samples, which led to drastically enhanced stability against Pt dissolution at high potentials.
- Kim, Dae-Suk,Kim, Cheonghee,Kim, Jung-Kon,Kim, Jun-Hyuk,Chun, Ho-Hwan,Lee, Hyunjoo,Kim, Yong-Tae
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- Hollow and cage-bell structured nanomaterials of noble metals
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Mastery of the structure of nanomaterials enables control of their properties to enhance their performance for a given application. Herein we demonstrate the synthesis of metal nanomaterials with hollow interiors or cage-bell structures based on the inside-out diffusion of Ag in core-shell structured nanoparticles. It begins with the synthesis of core-shell Ag-M or core-shell-shell MA-Ag-MB nanoparticles in an organic solvent. Ag is then extracted from the core or the inner shell by bis(p-sulfonatophenyl)phenylphosphane, which binds strongly with Ag(I)/Ag(0) to allow the complete removal of Ag in 24-48 h, leaving behind an organosol of hollow or cage-bell structured metal nanomaterials. Because of their relatively lower densities, which usually translate to a higher surface area than their solid counterparts, the hollow and cage-bell structured metal nanomaterials are especially relevant to catalysis. For example, cage-bell structured Pt-Ru nanoparticles were found to display outstanding methanol tolerance for the cathode reaction of direct methanol fuel cells (DMFCs) as a result of the differential diffusion of methanol and oxygen in the cage-bell structure.
- Liu, Hui,Qu, Jianglan,Chen, Yunfa,Li, Jianqiang,Ye, Feng,Lee, Jim Yang,Yang, Jun
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p. 11602 - 11610
(2012/09/05)
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- Platinum electrodeposition in porous silicon: The influence of surface solvation effects on a chemical reaction in a nanospace
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A chemical reaction in a nanospace is decelerated once a diffusion-limited condition is reached due to the difficulty in supply of reactants from the bulk. We illustrate how to overcome this problem for platinum electrodeposition within nanoporous silicon electrodes. The surface-induced hydration structure of reactants is essential. We make nanopore surfaces hydrophobic by covering them with organic molecules and adopt platinum complex ions with sufficiently large sizes as reactants. Due to the resulting fact that the ions are strongly excluded from the bulk solution to the surface, the ion concentration is greatly enriched within nanopores. This enrichment accelerates the reaction.
- Fukami, Kazuhiro,Koda, Ryo,Sakka, Tetsuo,Urata, Tomoko,Amano, Ken-Ichi,Takaya, Hikaru,Nakamura, Masaharu,Ogata, Yukio,Kinoshita, Masahiro
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- Smectite clays as the quasi-templates for platinum electrodeposition
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Smectite clays suspended in a platinum deposition solution are here shown to increase the specific surface area of electrodeposited Pt on gold and porous carbon paper supports, and to enhance the specific activity of Pt towards methanol oxidation under steady-state conditions. Organomodified natural bentonite shows a more pronounced effect with respect to natural montmorillonite and synthetic laponite. The effect of clay, as evidenced by microscopy and X-ray diffraction, is to decrease the average size of the Pt crystallites and simultaneously the degree of their mutual coalescence. This effect is associated with suppression of Pt secondary nucleation observed in deposition current transients, and the electrocatalytic activity is suggested to be affected by the intergrain boundaries.
- Lavrentyeva,Vassiliev,Levin,Tsirlin,Polyakov,Leoni,Napolskii,Petrii,Tsirlina
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- Intramolecular selective hydrogenation of cinnamaldehyde over CeO 2-ZrO2-supported Pt catalysts
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Selective liquid phase hydrogenation of cinnamaldehyde is reported, for the first time, over CeO2, ZrO2, and CeO2-ZrO 2-supported Pt catalysts. Cinnamyl alcohol is the selective product. These catalysts are highly active and selective even at 25 °C and found to be superior to most of the hitherto known supported Pt catalysts. Alkali addition (NaOH) has enhanced the performance of these catalysts. At an optimized reaction condition, 95.8% conversion of cinnamaldehyde and 93.4% selectivity of cinnamyl alcohol have been obtained. Acidity of the support (due to the presence of ZrO2 component) and higher electron density at Pt (due to CeO2 component) are attributed to be responsible for the superior catalytic activity of Pt supported on CeO2-ZrO2 composite material.
- Bhogeswararao,Srinivas
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- Regeneration mechanism of a Lean NOx Trap (LNT) catalyst in the presence of NO investigated using isotope labelling techniques
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The presence of NO during the regeneration period of a Pt-Ba/Al 2O3 Lean NOx Trap (LNT) catalyst modifies significantly the evolution of products formed from the reduction of stored nitrates, particularly nitrogen and ammonia. The use of isotope labelling techniques, feeding 14NO during the storage period and 15NO during regeneration allows us to propose three different routes for nitrogen formation based on the different masses detected during regeneration, i.e. 14N2 (m/e = 28), 14N 15N (m/e = 29) and 15N2 (m/e = 30). It is proposed that the formation of nitrogen via Route 1 involves the reaction between hydrogen and 14NOx released from the storage component to form 14NH3 mainly. Then, ammonia further reacts with 14NOx located downstream to form 14N2. In Route 2, it is postulated that the incoming 15NO reacts with hydrogen to form 15NH3 in the reactor zone where the trap has been already regenerated. This isotopically labelled ammonia travels through the catalyst bed until it reaches the regeneration front where it participates in the reduction of stored nitrates (14NOx) to form 14N15N. The formation of 15N2 via Route 3 is believed to occur by the reaction between incoming 15NO and H2. The modification of the hydrogen concentration fed during regeneration affects the relative importance of H2 or 15NH3 as reductants and thus the production of 14N2 via Route 1 and 14N15N via Route 2.
- Pereda-Ayo, Benat,Gonzalez-Velasco, Juan R.,Burch, Robbie,Hardacre, Christopher,Chansai, Sarayute
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p. 177 - 186
(2012/02/06)
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- Correlation of Pt-Re surface properties with reaction pathways for the aqueous-phase reforming of glycerol
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The surface properties of Pt-Re catalytic nanoparticles supported on carbon following exposure to a hydrogen reducing environment and subsequent hydrothermal conditions have been studied using in situ X-ray photoelectron spectroscopy (XPS) and ammonia temperature-programmed desorption (TPD). These properties have been correlated with the catalyst selectivity for the aqueous-phase reforming of glycerol. We show that Pt in reduced Pt-Re/C becomes electron deficient, and a fraction of the Re becomes oxidized when the catalyst is subsequently exposed to hydrothermal reaction conditions. Oxidation of Pt-Re generates surface acidity, which drastically affects the reaction pathways. The acid site concentration, but not acid site strength, increases with Re loading. This acidity increase with Re addition favors C-O over C-C cleavage, which results in higher selectivity to liquid products and alkanes at the expense of hydrogen selectivity. We propose a model for the Pt-Re active site and the origin of acidity enhanced by the addition of Re.
- Zhang, Liang,Karim, Ayman M.,Engelhard, Mark H.,Wei, Zhehao,King, David L.,Wang, Yong
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- Co-deposition of Pt and ceria anode catalyst in supercritical carbon dioxide for direct methanol fuel cell applications
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Pt and mixed Pt-ceria catalysts were deposited onto gas diffusion layers using supercritical fluid deposition (SFD) to fabricate thin layer electrodes for direct methanol fuel cells. Dimethyl (1,5-cyclooctadiene) platinum (II) (CODPtMe2) and tetrakis (2,2,6,6-tetramethyl 3,5-heptanedionato) cerium (IV) (Ce(tmhd)4) were used as precursors. Hydrogen-assisted Pt deposition was performed in compressed carbon dioxide at 60 °C and 17.2 MPa to yield high purity Pt on carbon-black based gas diffusion layers. During the preparation of the mixed Pt-ceria catalyst, hydrogen reduction of CODPtMe 2 to yield Pt catalyzed the deposition of ceria from Ce(tmhd) 4 enabling co-deposition at 150 °C. The catalyst layers were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope-energy dispersive spectral (SEM-EDS) analyses. Their electrochemical performance toward methanol oxidation was examined in half cell mode using a three electrode assembly as well as in fuel cell mode. The thin layer electrodes formed via SFD exhibited higher performance in fuel cell operations compared to those prepared by the conventional brush-paint method. Furthermore, the Pt-ceria catalyst with an optimized composition exhibited greater methanol oxidation activity than pure platinum.
- You, Eunyoung,Guzmán-Blas, Rolando,Nicolau, Eduardo,Aulice Scibioh,Karanikas, Christos F.,Watkins, James J.,Cabrera, Carlos R.
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p. 191 - 200
(2012/08/14)
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- Preparation and electrochemical characterization of nitrogen doped graphene by microwave as supporting materials for fuel cell catalysts
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A quick and efficient approach to prepare nitrogen doped graphene (NG) is proposed in this paper via microwave heating in NH3 atmosphere. Results show that graphene, as an allotrope of carbon, is a good microwave-absorbing material and can reach a high temperature in minutes, facilitating nitrogen incorporation into the structure under NH3. Elemental analysis and X-ray photoelectron spectroscope (XPS) verified the success of N-doping with the nitrogen content of 5.04 wt%. For comparison, both plain grapheme (G) and the NG were used as supporting materials for platinum to investigate their potential application in fuel cells. Transmission electron microscope (TEM) images showed that the NG improved the distribution of Pt particles. Themogravimetry (TG) and differential scanning calorimeters (DSC) revealed better thermal stability of the Pt/NG than that of the Pt/G. Furthermore, the Pt/NG catalysts exhibited higher electrochemical active surface area, methanol catalytic activity, and tolerance to CO poisoning than those of the Pt/G under fuel cell conditions. It suggests that the NG prepared by microwave synthesis has provided a new way to improve electrocatalytic activity in fuel cells.
- Xin, Yuchen,Liu, Jian-Guo,Jie, Xiao,Liu, Wenming,Liu, Fuqiang,Yin, Ying,Gu, Jun,Zou, Zhigang
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p. 354 - 358
(2012/02/14)
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- Ultrasonic electrodeposition of platinum nanoflowers and their application in nonenzymatic glucose sensors
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In the present study, Pt nanoflowers were fabricated on the bare Au electrodes by using template-free ultrasonic electrodeposition method. Scanning electron microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray detector as well as X-ray diffraction were used for the characterization. It was found that Pt nanoflowers were composed of metallic Pt. The electrocatalytic properties of the Pt nanoflowers electrode for glucose oxidation were investigated by cyclic voltammetry and differential pulse voltammetry. Cyclic voltammograms (CVs) results showed that the Pt nanoflowers electrode exhibited excellent catalytic activity towards glucose oxidation in neutral media. Differential pulse voltammograms (DPVs) results showed that at +0.03 V, the sensitivity of the electrode to glucose oxidation was 1.87 μA cm-2 mM-1 with a linear range from 1 mM to 16 mM and detection limit of 48 μM (signal-to-noise ratio of 3). In addition, the nonenzymatic glucose sensors exhibited excellent selectivity, stability and repeatability.
- Guo,Hong,Tang,Fang,Xu
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- Bi-functional TiO2 cemented Ag grid under layer for enhancing the photovoltaic performance of a large-area dye-sensitized solar cell
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A bi-functional TiO2 cemented Ag grid under layer for enhanced the photovoltaic performance of a large-area dye-sensitized solar cell (DSSC) is prepared with a simple way. The conductive printing paste contains micro-sized Ag powders and nano-sized TiO2 cementing agent. The conductive printing paste can be well cemented on the FTO glass and form high conductive grids with Ag powders sintered together by the nano-sized TiO2 particles. The formed conductive grid is protected with a TiO2 thin layer and TiO2 sol treatment to avoid the iodine corrosion. The addition of the TiO2 cemented conductive grid can decrease the internal resistance of the large-area dye-sensitized solar cell when it is prepared in the photo and counter electrodes. Furthermore, the protecting TiO2 thin layer and the TiO2 sol treatment can be done on the whole area of the large-area photo electrode to both play as the blocking under layer at the same time, which can also enhance the photovoltaic performance of the large-area dye-sensitized solar cell.
- Lan, Zhang,Wu, Jihuai,Lin, Jianming,Huang, Miaoliang
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p. 313 - 318
(2012/04/17)
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- Platinum nanoparticle-decorated carbon nanotube clusters on screen-printed gold nanofilm electrode for enhanced electrocatalytic reduction of hydrogen peroxide
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In the present study the electrocatalytic behavior of platinum nanoparticle-decorated multi-walled carbon nanotube clusters vertically aligned on a screen-printed gold nanofilm electrode substrate (SPGFE/MWCNTC/PtNP) toward hydrogen peroxide was intensively investigated. Oriented multi-walled carbon nanotube clusters (MWCNTC) were firstly well-organized onto the screen-printed gold film electrode (SPGFE) surface by covalent immobilization, and then platinum nanoparticles (PtNPs) dispersed on the MWCNTC structure were in situ synthesized by electrochemically reducing chloroplatinic acid. It was demonstrated that the MWCNTC/PtNP hybrid structure on the SPGFE substrate could significantly enhance the electrochemical reduction of hydrogen peroxide in neutral solutions. Compared with platinum nanoparticles loading on disordered multi-walled carbon nanotubes (SPGFE/MWCNT/PtNP), the proposed SPGFE/MWCNTC/PtNP exhibited more sensitive responses for hydrogen peroxide reduction. The fabricated electrode provided linear current responses for hydrogen peroxide in the concentration range from 5 to 2000 μM with a detection limit of 1.23 μM. The non-enzymatic sensor also offered good reproducibility and high selectivity for hydrogen peroxide detection. The carbon nanotube cluster/platinum nanoparticle hybrid system holds great promise as a scaffold to fabricate enzyme biosensors.
- Niu, Xiangheng,Zhao, Hongli,Chen, Chen,Lan, Minbo
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- Electrochemical synthesis of mesoporous Pt-Au binary alloys with tunable compositions for enhancement of electrochemical performance
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Mesoporous Pt-Au binary alloys were electrochemically synthesized from lyotropic liquid crystals (LLCs) containing corresponding metal species. Two-dimensional exagonally ordered LLC templates were prepared on conductive substrates from diluted surfactant solutions including water, a nonionic surfactant, ethanol, and metal species by drop-coating. Electrochemical synthesis using such LLC templates enabled the preparation of ordered mesoporous Pt-Au binary alloys without phase segregation. The framework composition in the mesoporous Pt-Au alloy was controlled simply by changing the compositional ratios in the precursor solution. Mesoporous Pt-Au alloys with low Au content exhibited well-ordered 2D hexagonal mesostructures, reflecting those of the original templates. With increasing Au content, however, the mesostructural order gradually decreased, thereby reducing the electrochemically active surface area. Wide-angle X-ray diffraction profiles, X-ray photoelectron spectra, and elemental mapping showed that both Pt and Au were atomically distributed in the frameworks. The electrochemical stability of mesoporous Pt-Au alloys toward methanol oxidation was highly improved relative to that of nonporous Pt and mesoporous Pt films, suggesting that mesoporous Pt-Au alloy films are potentially applicable as electrocatalysts for direct methanol fuel cells. Also, mesoporous Pt-Au alloy electrodes showed a highly sensitive amperometric response for glucose molecules, which will be useful in next-generation enzyme-free glucose sensors.
- Yamauchi, Yusuke,Tonegawa, Akihisa,Komatsu, Masaki,Wang, Hongjing,Wang, Liang,Nemoto, Yoshihiro,Suzuki, Norihiro,Kuroda, Kazuyuki
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p. 5100 - 5109
(2012/05/04)
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- Zinc oxide-zinc stannate core-shell nanorod arrays for CdS quantum dot sensitized solar cells
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Nanorod arrays of zinc oxide-zinc stannate core-shell photoelectrodes were prepared by a simple hydrothermal process and cadmium sulfide (CdS) quantum dot sensitized solar cells were fabricated. The photocurrent density of the core-shell photoelectrode was found to improve by ～2.4 times compared to ZnO nanorod photoelectrodes, due to improved surface area and charge transport in the core-shell photoelectrodes. With a thin layer of ZnS on the CdS quantum dot surface, the core-shell quantum dot sensitized solar cell demonstrated maximum power conversion efficiency of 1.24% under 1 sun illumination (AM1.5).
- Bora, Tanujjal,Kyaw, Htet H.,Dutta, Joydeep
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p. 141 - 145
(2012/06/30)
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- Enhanced efficiency in dye sensitized solar cells with nanostructured Pt decorated multiwalled carbon nanotube based counter electrode
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Nanostructured Pt decorated functionalized multiwalled carbon nanotubes (Pt/f-MWNTs) cast on fluorine doped tin oxide coated glass (FTO) is demonstrated as a novel counter electrode (CE) for dye sensitized solar cells (DSSCs). Pt particles (20 wt.%, size a facile microwave assisted polyol reduction method. The DSSC fabricated with Pt/f-MWNTs CE (effective Pt loading ～10 μg cm-2) exhibits an enhanced efficiency of ～5.4% (under an illumination of AM 1.5 G, 100 mW cm-2), compared to ～2.3% and 4.5% for f-MWNTs and Pt CE based reference DSSCs. The CEs are fabricated without using conventional binders using a simple doctor blade method. A new equivalent circuit is proposed to model the electrochemical impedance behavior of porous f-MWNTs based CE. On the other hand, the behavior Pt/f-MWNTs based electrode is similar to that of Pt nanoparticles but with higher catalytic activity. Cyclic voltammetry studies reveal that Pt/f-MWNTs counter electrode offers greater catalytic surface area and facilitates faster reaction at its surface.
- Kaniyoor, Adarsh,Ramaprabhu, Sundara
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p. 199 - 206
(2012/07/14)
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- Solvent effect on the size of platinum nanoparticle synthesized in microemulsion systems
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In this research work, the effect of solvent on the size of paltinum nanoparticles synthesized by microemulsion method was investigated. Platinum nanoparticles have been prepared by the reduction of H2PtCl 6 with hydrazine in water-i
- Salabat, Alireza,Far, Mina Rahmati
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p. 881 - 883
(2012/08/28)
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