80937-33-3Relevant articles and documents
Adsorption and reactivity of nitrogen oxides (NO2, NO, N2O) on Fe-zeolites
Rivallan, Mickael,Ricchiardi, Gabriele,Bordiga, Silvia,Zecchina, Adriano
, p. 104 - 116 (2009)
Nitrous oxide decomposition and temperature programmed desorption tests on Fe-ZSM-5 and Fe-silicalite show that the catalytic conversion mechanism of N2O into N2 and O2 over Fe-zeolites is more complex than expected. Nitro
Decomposition of Nitrous Oxide on Palladium Crystal Planes
Eley, Daniel D.,Klepping, Anthony H.,Moore, Peter B.
, (1985)
The catalysed decomposition of N2O in the range 830 - 1000 K and 0.05 - 1.0 Torr (1 Torr ca. 133 Pa) has been examined on Pd single-crystal surfaces and polycrystalline wires and compared with earlier work.The relative reaction velocities at 1000 deg K an
Reversible O2 binding to a dinuclear copper(I) complex with linked tris(2-pyridylmethyl)amine units: Kinetic-thermodynamic comparisons with mononuclear analogues
Lee, Dong-Heon,Wei, Ning,Murthy, Narasimha N.,Tyeklár, Zoltán,Karlin, Kenneth D.,Kaderli, Susan,Jung, Bernhard,Zuberbühler, Andreas D.
, p. 12498 - 12513 (1995)
The kinetics and thermodynamics of reaction of O2 with copper(I) complexes can provide fundamental information relevant to chemical and biological systems. Using diode-array variable-temperature (180-296 K) stopped-flow kinetic methods, we report detailed information on the O2 reactivity (in EtCN) of dicopper(I) complex [(D1)Cu(I)2(RCN)2]2+ (2a) (R = Me or Et) [D1 = dinucleating ligand with a -CH2CH2- group linking two tris(2-pyridylmethyl)amine (TMPA) units at a 5-pyridyl position of each tetradentate moiety]. A comparative study of mononuclear complex [(TMPAE)Cu(RCN)]+ (1a') [TMPAE has a -C(O)OCH3 ester substituent in the 5-position of one pyridyl group of TMPA] has been carried out. The results are compared with data from the previously investigated complex [(TMPA)Cu(RCN)]+ (1a). The syntheses of D1 and 2a-(ClO4)2 are described; an X-ray structure reveals two pentacoordinate Cu(I) ions (Cu···Cu = 11.70 A?), each bound by the N4-tetradentate and an EtCN molecule. Cyclic voltammetric data for 1a' and 2a are reported. At 193 K in EtCN, 2a reacts with O2 (Cd/C2 = 2:1, manometry) to produce an intensely purple colored solution of adduct [(D1)Cu2(O2)]2+ (2c), λ(max) = 540 nm (ε = 11 100 M-1 cm-1). This peroxo-dicopper(II) species reacts with PPh3, liberating O2 and producing the isolatable bis-phosphine adduct [(D1)Cu2(PPh3)2]2+. The kinetic investigation provides spectral characterization of transient Cu/O2 1:1 adducts generated upon oxygenation of cold solutions of 1a' or 2a. [(TMPAE)Cu(O2)]+ (1b') forms reversibly (λ(max) = 415 nm) with k1 = (8.2 ± 0.4) x 103 M-1 s-1 and K1 = k1/k-1 = (284 ± 9) M-1 at 183 K, with ΔH1° = (-32 ± 1) kJ mol-1, ΔS1° = (-127 ± 3) J K-1 mol-1. Two types of Cu(II)-O2- complexes form in the reaction of 2a: a 2:1 open form (i.e., [(D1)Cu2(O2)(EtCN)]2+, 2b) and a bis-O2 2:2 open adduct (i.e., [(D1)Cu2(O2)2]2+, 2b'). For the formation of 2b, k1 = (1.63 ± 0.01) x 104 M-1 s-1 and K1 = (2.03 ± 0.04) x 103 M-1 at 183 K. Complexes 2b and 2b' have identical spectroscopic properties (λ(max) = 416 nm, ? = 4500 M-1 cm-1) per Cu-O2 unit, and their rate constants are statistically related. Intermediates 1b' and 2b further convert into (μ-peroxo)dicopper(II) [(2 Cu):(1O2)] complexes. [{(TMPAE)Cu}2(O2)]2+ (1c') (λ(max) = 532 nm, ? = 9380 M-1 cm-1) forms in a second-order reaction of 1b' with 1a' with K1K2 = (2.1 ± 0.4) x 1011 M-2 at 183 K (ΔH12° = -77 ± 1 kJ mol-1 and AS12° = -203 ± 5 J K-1 mol-1), while [(D1)Cu2(O2)]2+ (2c) (λ(max) = 540 nm, ? = 11 100 M-1 cm-1) is generated from 2b in an intramolecular reaction,with k2 = (3.51 ± 0.05) x 101 s-1 and k(on) = k1k2/k-1 = (7.1 ± 0.2) x 104 M-1 s-1 (183 K). The overall formation of 2c is faster than for 1c' or [{(TMPA)Cu}2(O2)]2+ (1c) because of a more positive entropy of activation (ΔS(on)paragraph = (-139 ± 3) J K-1 mol-1 for 2c vs ΔS(on)paragraph = (-201 ± 5) J K-1 mol-1 for 1c). However, this significantly enhanced kinetic reactivity (for 2a → 2c) is not reflected by an analogous increase in thermodynamic stability. [(D1)Cu2(O2)]2+ (2c) is enthalpically less stable (ΔH12° = (-34.8 ± 0.4) kJ -1) than Cu2O2 species 1c and 1c' (ΔH12° = -81 to -77 kJ mol-1, respectively), which are formed from mononuclear precursors. There is a substantially larger overall formation entropy for 2c [ΔS12° = (-89.3 ± 1.5) J K-1 mol-1 compared to -220 and -203 J K-1 mol-1 for 1c and 1c', respectively] since Cu2O2 formation is an intramolecular, rather than intermolecular, process. Examination of other kinetic parameters and spectral differences provides complementary information that 2c has a strained structure. In fact, 2c is not the ultimate oxidation product: relief of steric constraints occurs at higher temperatures by a slow rearrangement (λ(max) = 540 nm → λ(max) = 529 nm) producing {Cu2O2}(n) oligomers containing intermolecular Cu-O2-Cu bonds. A particularly stable trimer species [{(D1)Cu2(O2)}3]6+ (2d) was characterized, with ΔH3° = (-153 kJ mol-1)/3 = -51 kJ mol-1 per Cu2O2 unit, intermediate between that seen for 2c, 1c, and 1c'.
Adsorbed Oxygen Species Formed by the Decomposition of N2O on Li/MgO Catalysts
Nakamura, Masato,Yanagibashi, Hiroshi,Mitsuhashi, Hiroyuki,Takezawa, Nobutsune
, p. 2467 - 2472 (1993)
A considerable amount of adsorbed oxygen species were produced by the decomposition of N2O on Li/MgO.The amount of the oxygen species greatly increases by Li(I)-doping on MgO.Over 0.7 wtpercent Li/MgO, the amount of the oxygen species formed was 10.67 μmol m-2.The temperature-programmed desorption of the oxygen species revealed that two types of adsorbed oxygen species were present on Li/MgO; one (α-oxygen species) desorbed in proportion to the second order in the amount of the adsorbed species with an activation energy of 141 kJ mol-1, giving a peak (α-oxygen peak) at 673-693 K; the other (β-oxygen species) desorbed in proportion to the first order in the amount of the adsorbed species with an activation energy of 219 kJ mol-1, giving a peak (β-oxygen peak) at 753-768 K.A weak α-oxygen peak occurred on MgO and no β-oxygen peak was discerned.On Li/MgO, a β-oxygen peak appeared along with an α-oxygen peak.At higher Li-loadings the β-oxygen peak was more intense than the α-oxygen peak.The sites for these oxygen species were suggested to be derived by the addition of Li(I) on MgO.It was suggested that the α-oxygen species were present at the surface sites on higher index faces of MgO, whereas the β-oxygen species were present at oxygen vacancies in the vicinity of Li(I) substituting for Mg(II).The hydrolysis of these adsorbed oxygen species yielded an appreciable amount of H2O2, suggesting that these species were primarilly present as surface peroxide on MgO and Li/MgO.
Kinetics of N2O Decomposition on the Surface of γ-Al2O3 doped with Sodium Ions
Kordulis, Christos,Vordonis, Leonidas,Lycourghiotis, Alexis,Pomonis, Phillipos
, p. 627 - 634 (1987)
The kinetics of N2O decomposition on a series of specimens prepared by doping γ-Al2O3 with various amounts of Na+ ions has been studied at various temperatures using a flow-bed reactor working under atmospheric pressure.This doping promotes the adsorption of oxygen anions produced from surface decomposition, presumably via the formation of surface species +...O-...Na+>, bringing about a transformation of the rate equation from R=k into R=kbN2OPN2O/bO2P1/2O2 (where bN2O and bO2 are adsorption coefficients and PN2O and PO2 are partial pressures).Moreover, a decrease in catalytic activity, expressed either as fractional conversion or rate of reaction, was observed on increasing the surface coverage C, of γ-Al2O3 with Na+ ions determined by X-ray photoelectron spectroscopy.Specifically, the dependence of the catalytic activity on the surface coverage of γ-Al2O3 is described by the relationship 1n(1/R) = 15.4+(281/K)C (where K is a proportionality constant) and it was concluded that the deactivation observed is due to the promotion of the O2 adsorption caused by the Na+ ions.Finally, the linear dependence of the surface coverage of γ-Al2O3 on the sodium content strongly suggests that the dispersion of the sodium supported species is constant irrespective of the surface concentration of sodium.
The RuII(OH2)-RuIV(O) Couple in a Ruthenium Complex of 2-(Phenylazo)pyridine: Homogeneous Catalysis of the Oxidation of Water to Dioxygen
Goswami, Sreebrata,Chakravarty, Akhil R.,Chakravorty, Animesh
, p. 1288 - 1289 (1982)
In acidic solution II(OH2)(py)L2>2+ can be oxidised to IV(O)(py)L2>2+ in a single reversible step (E0298 = 1.20 V) and the oxidised complex catalyses the dehydrogenation of water to dioxygen in the presence of Ce4+ .
Electrocatalytic Water Oxidation with α-[Fe(mcp)(OTf)2] and Analogues
D'Agostini, Silvia,Kottrup, Konstantin G.,Casadevall, Carla,Gamba, Ilaria,Dantignana, Valeria,Bucci, Alberto,Costas, Miquel,Lloret-Fillol, Julio,Hetterscheid, Dennis G.H.
, p. 2583 - 2595 (2021/03/03)
The complex α-[Fe(mcp)(OTf)2] (mcp = N,N′-dimethyl-N,N′-bis(pyridin-2-ylmethyl)-cyclohexane-1,2-diamine and OTf = trifluoromethanesulfonate anion) was reported in 2011 by some of us as an active water oxidation (WO) catalyst in the presence of sacrificial oxidants. However, because chemical oxidants are likely to take part in the reaction mechanism, mechanistic electrochemical studies are critical in establishing to what extent previous studies with sacrificial reagents have actually been meaningful. In this study, the complex α-[Fe(mcp)(OTf)2] and its analogues were investigated electrochemically under both acidic and neutral conditions. All the systems under investigation proved to be electrochemically active toward the WO reaction, with no major differences in activity despite the structural changes. Our findings show that WO-catalyzed by mcp-iron complexes proceeds via homogeneous species, whereas the analogous manganese complex forms a heterogeneous deposit on the electrode surface. Mechanistic studies show that the reaction proceeds with a different rate-determining step (rds) than what was previously proposed in the presence of chemical oxidants. Moreover, the different kinetic isotope effect (KIE) values obtained electrochemically at pH 7 (KIE ～10) and at pH 1 (KIE = 1) show that the reaction conditions have a remarkable effect on the rds and on the mechanism. We suggest a proton-coupled electron transfer (PCET) as the rds under neutral conditions, whereas at pH 1 the rds is most likely an electron transfer (ET).
Syntheses, characterizationsna and water-electrolysis properties of 2D α- and β-PdSeO3 bulk and nanosheet semiconductors
Wu, Yusheng,Wang, Lin,Zhang, Hongyan,Ding, Jie,Han, Min,Fang, Min,Bao, Jianchun,Wu, Yong
, (2021/02/16)
In contrast to alkaline water electrolysis, water electrolysis in an acidic environment has higher energy efficiency, more compact cell design, higher gas purity, and less sensitivity to environmental impurity. Herein, the syntheses of the known 2D α- and β-PdSeO3 were improved. The bulk materials were exfoliated into nanosheets using an ultrasonic-assisted liquid-phase exfoliation similar to that of preparing graphene nanosheets. Their band-gaps, valence band maximums (VBMs) and conduction band minimums (CBMs) were determined using Mott-Schottky plots and the linear potential scan method in acidic aqueous solution, 0.2 ?M Na2SO4 aqueous solution and non-aqueous solution. Their transient photocurrent properties were also examined, along with their Electrochemical Impedance Spectra (EIS). The bulk materials are stable in pH ?= ?0–14 value water solution for at least 48 ?h. α- and β-PdSeO3 nanosheets exhibit moderate catalytic activities for hydrogen evolution reactions in 0.5 ?M ?H2SO4 (η10 (overpotential at 10 ?mA ?cm-2: 185 and 209 ?mV, respectively; catalyst loading: 0.28 ?mg ?cm-2), much better than the performances of the bulk materials. In addition, β-PdSeO3 bulk and nanosheets materials show good and similar OER catalytic activities in 0.5 ?M ?H2SO4 (η10: 381 and 405 ?mV, respectively; catalyst loading: 0.28 ?mg ?cm-2). Thus, β-PdSeO3 nanosheets were found to be a good overall water splitting catalyst in acidic solution. The above catalysts all show long-term stability. In contrast, α-PdSeO3 does not have OER catalytic property. To our knowledge, Pd-based acidic overall water splitting catalysts are very rare.
