13767-16-3Relevant articles and documents
Catalytic Hydrogenation of a Manganese(V) Nitride to Ammonia
Kim, Sangmin,Zhong, Hongyu,Park, Yoonsu,Loose, Florian,Chirik, Paul J.
, p. 9518 - 9524 (2020)
The catalytic hydrogenation of a metal nitride to produce free ammonia using a rhodium hydride catalyst that promotes H2 activation and hydrogen-atom transfer is described. The phenylimine-substituted rhodium complex (η5-C5Me5)Rh(MePhI)H (MePhI = N-methyl-1-phenylethan-1-imine) exhibited higher thermal stability compared to the previously reported (η5-C5Me5)Rh(ppy)H (ppy = 2-phenylpyridine). DFT calculations established that the two rhodium complexes have comparable Rh-H bond dissociation free energies of 51.8 kcal mol-1 for (η5-C5Me5)Rh(MePhI)H and 51.1 kcal mol-1 for (η5-C5Me5)Rh(ppy)H. In the presence of 10 mol% of the phenylimine rhodium precatalyst and 4 atm of H2 in THF, the manganese nitride (tBuSalen)MnN underwent hydrogenation to liberate free ammonia with up to 6 total turnovers of NH3 or 18 turnovers of H? transfer. The phenylpyridine analogue proved inactive for ammonia synthesis under identical conditions owing to competing deleterious hydride transfer chemistry. Subsequent studies showed that the use of a non-polar solvent such as benzene suppressed formation of the cationic rhodium product resulting from the hydride transfer and enabled catalytic ammonia synthesis by proton-coupled electron transfer.
Direct Electrochemical Ammonia Synthesis from Nitric Oxide
Chen, Shiming,Deng, Dehui,Fu, Xiaoyan,Guo, Chenxi,Long, Jun,Xiao, Jianping,Zhang, Yunlong
, p. 9711 - 9718 (2020)
NO removal from exhausted gas is necessary owing to its damage to environment. Meanwhile, the electrochemical ammonia synthesis (EAS) from N2 suffers from low reaction rate and Faradaic efficiency (FE). Now, an alternative route for ammonia synthesis is proposed from exhaust NO via electrocatalysis. DFT calculations indicate electrochemical NO reduction (NORR) is more active than N2 reduction (NRR). Via a descriptor-based approach, Cu was screened out to be the most active transition metal catalyst for NORR to NH3 owing to its moderate reactivity. Kinetic barrier calculations reveal NH3 is the most preferred product relative to H2, N2O, and N2 on Cu. Experimentally, a record-high EAS rate of 517.1 μmol cm?2 h?1 and FE of 93.5 percent were achieved at ?0.9 V vs. RHE using a Cu foam electrode, exhibiting stable electrocatalytic performances with a 100 h run. This work provides an alternative strategy to EAS from exhaust NO, coupled with NO removal.
Self-organized Ruthenium–Barium Core–Shell Nanoparticles on a Mesoporous Calcium Amide Matrix for Efficient Low-Temperature Ammonia Synthesis
Kitano, Masaaki,Inoue, Yasunori,Sasase, Masato,Kishida, Kazuhisa,Kobayashi, Yasukazu,Nishiyama, Kohei,Tada, Tomofumi,Kawamura, Shigeki,Yokoyama, Toshiharu,Hara, Michikazu,Hosono, Hideo
, p. 2648 - 2652 (2018)
A low-temperature ammonia synthesis process is required for on-site synthesis. Barium-doped calcium amide (Ba-Ca(NH2)2) enhances the efficacy of ammonia synthesis mediated by Ru and Co by 2 orders of magnitude more than that of a conventional Ru catalyst at temperatures below 300 °C. Furthermore, the presented catalysts are superior to the wüstite-based Fe catalyst, which is known as a highly active industrial catalyst at low temperatures and pressures. Nanosized Ru–Ba core–shell structures are self-organized on the Ba-Ca(NH2)2 support during H2 pretreatment, and the support material is simultaneously converted into a mesoporous structure with a high surface area (>100 m2 g?1). These self-organized nanostructures account for the high catalytic performance in low-temperature ammonia synthesis.
Single-atom metal-N4site molecular electrocatalysts for ambient nitrogen reduction
Sun, Sai,Yang, Xiaoxuan,Li, Siqi,Chen, Xinyu,Li, Ke,Lv, Jiaqi,Wang, Wenwen,Cheng, Dongming,Wang, Yong-Hui,Zang, Hong-Ying
, p. 2589 - 2596 (2021)
Electrochemical N2reduction to NH3is an emerging energy technology, attracting much attention due to its features of mild reaction conditions and being non-polluting. In this work, we demonstrate that a well-defined cobalt tetraphenylporphyrin (CoTPP) molecule as a model catalyst exhibits good electrocatalytic nitrogen reduction activity in 0.1 M HCl electrolyte with an ammonia yield of 15.18 ± 0.78 μg h-1mg-1cat.calculated by the indophenol blue method and a Faraday efficiency (FE) of 11.43 ± 0.74%. The catalyst also has satisfactory electrolytic stability and recycling test reusability. The activity displayed by the porphyrin molecular catalysts is attributed to the full exposure of the metal-N4sites. To trace the source of ammonia, an isotope labeling experiment (15N2as the feed gas) is used to calculate the ammonia yieldvia1H nuclear magnetic resonance (NMR), which is close to that of the indophenol blue method. In addition, we replace the central metal to prepare CuTPP and MnTPP, and they also show electrocatalytic nitrogen reduction reaction (NRR) ability. This work proves the feasibility and versatility of using metalloporphyrin molecules as model electrocatalysts for NRR and offers a new strategy for the further development of molecular NRR catalysts.
Schottky Barrier-Induced Surface Electric Field Boosts Universal Reduction of NOx? in Water to Ammonia
Gao, Peng,Xue, Zhong-Hua,Zhang, Shi-Nan,Xu, Dong,Zhai, Guang-Yao,Li, Qi-Yuan,Chen, Jie-Sheng,Li, Xin-Hao
, p. 20711 - 20716 (2021)
NOx? reduction acts a pivotal part in sustaining globally balanced nitrogen cycle and restoring ecological environment, ammonia (NH3) is an excellent energy carrier and the most valuable product among all the products of NOx? reduction reaction, the selectivity of which is far from satisfaction due to the intrinsic complexity of multiple-electron NOx?-to-NH3 process. Here, we utilize the Schottky barrier-induced surface electric field, by the construction of high density of electron-deficient Ni nanoparticles inside nitrogen-rich carbons, to facilitate the enrichment and fixation of all NOx? anions on the electrode surface, including NO3? and NO2?, and thus ensure the final selectivity to NH3. Both theoretical and experimental results demonstrate that NOx? anions were continuously captured by the electrode with largely enhanced surface electric field, providing excellent Faradaic efficiency of 99 % from both electrocatalytic NO3? and NO2? reduction. Remarkably, the NH3 yield rate could reach the maximum of 25.1 mg h?1 cm?2 in electrocatalytic NO2? reduction reaction, outperforming the maximum in the literature by a factor of 6.3 in neutral solution. With the universality of our electrocatalyst, all sorts of available electrolytes containing NOx? pollutants, including seawater or wastewater, could be directly used for ammonia production in potential through sustainable electrochemical technology.
Ammonia Synthesis Under Ambient Conditions: Selective Electroreduction of Dinitrogen to Ammonia on Black Phosphorus Nanosheets
Zhang, Lili,Ding, Liang-Xin,Chen, Gao-Feng,Yang, Xianfeng,Wang, Haihui
, p. 2612 - 2616 (2019)
Constructing efficient catalysts for the N2 reduction reaction (NRR) is a major challenge for artificial nitrogen fixation under ambient conditions. Herein, inspired by the principle of “like dissolves like”, it is demonstrated that a member of the nitrogen family, well-exfoliated few-layer black phosphorus nanosheets (FL-BP NSs), can be used as an efficient nonmetallic catalyst for electrochemical nitrogen reduction. The catalyst can achieve a high ammonia yield of 31.37 μg h?1 mg?1cat. under ambient conditions. Density functional theory calculations reveal that the active orbital and electrons of zigzag and diff-zigzag type edges of FL-BP NSs enable selective electrocatalysis of N2 to NH3 via an alternating hydrogenation pathway. This work proves the feasibility of using a nonmetallic simple substance as a nitrogen-fixing catalyst and thus opening a new avenue towards the development of more efficient metal-free catalysts.
Isomers of disulfur dinitride, S2N2
Zeng, Xiaoqing,Beckers, Helmut,Willner, Helge,Antognini, Andrea Flores
, p. 2758 - 2761 (2015)
UV photolysis (λ=248 or 255 nm) of cyclic S2N2 isolated in solid argon matrices yields two open-shell S2N2 isomers, trans SNSN (3A″ ) and cis SNSN (3A″), as well as a closed-shell C2v dimer (SN)2 (1A1). These novel isomers have been characterized by their IR spectra and mutual photointerconversion reactions. Quantum chemical calculations support the experimental results and also provide insight into the complex potential energy surface of S2N2.
A five-coordinate phosphino/acetate iron(II) scaffold that binds N 2, N2H2, N2H4, and NH3 in the sixth site
Saouma, Caroline T.,Moore, Curtis E.,Rheingold, Arnold L.,Peters, Jonas C.
, p. 11285 - 11287 (2011)
A family of iron(II) complexes that coordinate dinitrogen, diazene, hydrazine, and ammonia are presented. This series of complexes is unusual in that the complexes within it feature a common auxiliary ligand set and differ only by virtue of the nitrogenou
Highly ordered Nb2O5 nanochannel film with rich oxygen vacancies for electrocatalytic N2 reduction: Inactivation and regeneration of electrode
Wang, Jialu,Kang, Shenghong,Zhu, Xiaoguang,Wang, Guozhong,Zhang, Haimin
, p. 2833 - 2836 (2021)
We report the fabrication of highly ordered Nb2O5 nanochannel film (Nb2O5-NCF) onto niobium foil by an anodization method. After thermal treatment, the obtained Nb2O5-NCF with rich oxygen vacancies exhibits electrochemical N2 reduction reaction (NRR) activity with an NH3 yield rate of 2.52 × 10?10 mol cm-2 s-1 and a faradaic efficiency of 9.81% at ?0.4 V (vs. RHE) in 0.1 mol/L Na2SO4 electrolyte (pH 3.2). During electrocatalytic NRR, the Nb2O5-NCF takes place electrochromism (EC), along with a crystalline phase transformation from pseudo hexagonal phase to hexagonal phase owing to H+ insertion. This results in the reduced NRR activity due to the decrease of oxygen vacancies of hexagonal phase Nb2O5, which can be readily regenerated by low-temperature thermal treatment or applying an anodic potential, showing superior recycling reproducibility.
A Janus Fe-SnO2 Catalyst that Enables Bifunctional Electrochemical Nitrogen Fixation
Chen, Lin,Cong, Meiyu,Ding, Xin,Jin, Yu,Wang, Yong,Xu, Fanfan,Zhang, Linlin,Zhang, Lixue
, p. 10888 - 10893 (2020)
Electrochemical N2 reduction reactions (NRR) and the N2 oxidation reaction (NOR), using H2O and N2, are a sustainable approach to N2 fixation. To date, owing to the chemical inertness of nitrogen, emerging electrocatalysts for the electrochemical NRR and NOR at room temperature and atmospheric pressure remain largely underexplored. Herein, a new-type Fe-SnO2 was designed as a Janus electrocatalyst for achieving highly efficient NRR and NOR catalysis. A high NH3 yield of 82.7 μg h?1 mgcat.?1 and a Faraday efficiency (FE) of 20.4 percent were obtained for NRR. This catalyst can also serve as an excellent NOR electrocatalyst with a NO3? yields of 42.9 μg h?1 mgcat.?1 and a FE of 0.84 percent. By means of experiments and DFT calculations, it is revealed that the oxygen vacancy-anchored single-atom Fe can effectively adsorb and activate chemical inert N2 molecules, lowering the energy barrier for the vital breakage of N≡N and resulting in the enhanced N2 fixation performance.
Altering Hydrogenation Pathways in Photocatalytic Nitrogen Fixation by Tuning Local Electronic Structure of Oxygen Vacancy with Dopant
Bo, Yanan,Du, Pengye,Gao, Chao,Hu, Canyu,Hu, Yangguang,Li, Yu,Lin, Yunxiang,Liu, Zhi,Long, Ran,Song, Li,Wang, Haiyun,Wu, Xiaojun,Xiong, Yujie,Yang, Tian,Ye, Bangjiao,Ye, Run
, p. 16085 - 16092 (2021)
To avoid the energy-consuming step of direct N≡N bond cleavage, photocatalytic N2 fixation undergoing the associative pathways has been developed for mild-condition operation. However, it is a fundamental yet challenging task to gain comprehensive understanding on how the associative pathways (i.e., alternating vs. distal) are influenced and altered by the fine structure of catalysts, which eventually holds the key to significantly promote the practical implementation. Herein, we introduce Fe dopants into TiO2 nanofibers to stabilize oxygen vacancies and simultaneously tune their local electronic structure. The combination of in situ characterizations with first-principles simulations reveals that the modulation of local electronic structure by Fe dopants turns the hydrogenation of N2 from associative alternating pathway to associative distal pathway. This work provides fresh hints for rationally controlling the reaction pathways toward efficient photocatalytic nitrogen fixation.
Surface-nitrogen removal in a steady-state NO + H2 reaction on Pd(110)
Ma, Yunsheng,Matsushima, Tatsuo
, p. 1256 - 1261 (2005)
Surface-nitrogen removal steps were analyzed in the course of a catalyzed NO + H2 reaction on Pd(110) by angle-resolved mass spectroscopy combined with cross-correlation time-of-flight techniques. Four removal steps, i.e., (i) the associative process of nitrogen atoms, 2N(a) → N 2(g), (ii) the decomposition of the intermediate, NO(a) + N(a) → N2O(a) → N2(g) + O(a), (iii) its desorption, N 2O(a) → N2O(g), and (iv) the desorption as ammonia, N(a) + 3H(a) → NH3(g), are operative in a comparable order. Above 600 K, process (i) is predominant, whereas the others largely contribute below 600 K. Process (iv) becomes significant at H2 pressures above a critical value, about half the NO pressure. Hydrogen was a stronger reagent than CO toward NO reduction and relatively enhanced the N(a) associative process.
Iodonitrene in Action: Direct Transformation of Amino Acids into Terminal Diazirines and 15N2-Diazirines and Their Application as Hyperpolarized Markers
Colell, Johannes F. P.,Franck, Xavier,Glachet, Thomas,Marzag, Hamid,Reboul, Vincent,Saraiva Rosa, Nathalie,Theis, Thomas,Warren, Warren S.,Zhang, Guannan
, (2019)
A one-pot metal-free conversion of unprotected amino acids to terminal diazirines has been developed using phenyliodonium diacetate (PIDA) and ammonia. This PIDA-mediated transformation occurs via three consecutive reactions and involves an iodonitrene intermediate. This method is tolerant to most functional groups found on the lateral chain of amino acids, it is operationally simple, and it can be scaled up to provide multigram quantities of diazirine. Interestingly, we also demonstrated that this transformation could be applied to dipeptides without racemization. Furthermore, 14N2 and 15N2 isotopomers can be obtained, emphasizing a key trans-imination step when using 15NH3. In addition, we report the first experimental observation of 14N/15N isotopomers directly creating an asymmetric carbon. Finally, the 15N2-diazirine from l-tyrosine was hyperpolarized by a parahydrogen-based method (SABRE-SHEATH), demonstrating the products' utility as hyperpolarized molecular tag.
Two-Dimensional Supramolecular Nanoarchitectures of Polypseudorotaxanes Based on Cucurbit[8]uril for Highly Efficient Electrochemical Nitrogen Reduction
Zhang, Cai-Cai,Liu, Xiaolu,Liu, Yu-Ping,Liu, Yu
, p. 8724 - 8732 (2020)
Supramolecular assemblies with two-dimensional (2D) topology have drawn great attraction in the development of functional materials through a modular approach. Herein, a novel organic 2D polypseudorotaxane has been constructed on the basis of cucurbit[8]uril (CB[8]) through host-stabilized charge-transfer (CT) interactions of naphthol-modified porphyrin (TPP-Np) and viologen derivatives (DMV). Interestingly, the 2D polypseudorotaxanes could serve as a platform for preparation of ultrafine Pt nanoparticles with favorable and homogeneous dispersion through a simple self-metallized process, leading to the formation of supramolecular hybrid materials (PtNPs@(CB[8]/DMV/TPP-Np)). Surprisingly, the PtNPs@(CB[8]/DMV/TPP-Np) could be applied to efficient electrochemical nitrogen reduction reaction, with a NH3 yield rate up to 23.2 μg h-1 mgPt-1 at -0.2 V versus a reversible hydrogen electrode under ambient conditions. Notably, our results not only demonstrate the feasible construction of 2D polypseudorotaxanes but also deepen the understanding of structure-activity relationships in supramolecular nanoarchitectures, as well as pave an effective and low-energy input strategy for artificial nitrogen fixation.
B?N Pairs Enriched Defective Carbon Nanosheets for Ammonia Synthesis with High Efficiency
Chen, Chen,Yan, Dafeng,Wang, Yu,Zhou, Yangyang,Zou, Yuqin,Li, Yafei,Wang, Shuangyin
, (2019)
Electrochemical synthesis has garnered attention as a promising alternative to the traditional Haber–Bosch process to enable the generation of ammonia (NH3) under ambient conditions. Current electrocatalysts for the nitrogen reduction reaction (NRR) to produce NH3 are comprised of noble metals or transitional metals. Here, an efficient metal-free catalyst (BCN) is demonstrated without precious component and can be easily fabricated by pyrolysis of organic precursor. Both theoretical calculations and experiments confirm that the doped B?N pairs are the active triggers and the edge carbon atoms near to B?N pairs are the active sites toward the NRR. This doping strategy can provide sufficient active sites while retarding the competing hydrogen evolution reaction (HER) process; thus, NRR with high NH3 formation rate (7.75 μg h?1 mgcat.?1) and excellent Faradaic efficiency (13.79%) are achieved at ?0.3 V versus reversible hydrogen electrode (RHE), exceeding the performance of most of the metallic catalysts.
Surface-Regulated Rhodium–Antimony Nanorods for Nitrogen Fixation
Hu, Zhiwei,Huang, Xiaoqing,Li, Leigang,Shao, Qi,Wang, Juan,Xiao, Xiangheng,Zhang, Nan
, p. 8066 - 8071 (2020)
Surface regulation is an effective strategy to improve the performance of catalysts, but it has been rarely demonstrated for nitrogen reduction reaction (NRR) to date. Now, surface-rough Rh2Sb nanorod (RNR) and surface-smooth Rh2Sb NR (SNR) were selectively created, and their performance for NRR was investigated. The high-index-facet bounded Rh2Sb RNRs/C exhibit a high NH3 yield rate of 228.85±12.96 μg h?1 mg?1Rh at ?0.45 V versus reversible hydrogen electrode (RHE), outperforming the Rh2Sb SNRs/C (63.07±4.45 μg h?1 mg?1Rh) and Rh nanoparticles/C (22.82±1.49 μg h?1 mg?1Rh), owing to the enhanced adsorption and activation of N2 on high-index facets. Rh2Sb RNRs/C also show durable stability with negligible activity decay after 10 h of successive electrolysis. The present work demonstrates that surface regulation plays an important role in promoting NRR activity and provides a new strategy for creating efficient NRR electrocatalysts.
Boosting Electrocatalytic Ammonia Production through Mimicking “π Back-Donation”
Lv, Chade,Zhong, Lixiang,Yao, Yao,Liu, Daobin,Kong, Yi,Jin, Xiaoli,Fang, Zhiwei,Xu, Wenjie,Yan, Chunshuang,Dinh, Khang Ngoc,Shao, Minhua,Song, Li,Chen, Gang,Li, Shuzhou,Yan, Qingyu,Yu, Guihua
, p. 2690 - 2702 (2020)
Electrocatalytic dinitrogen reduction reaction (N2RR) is an emerging route for ammonia synthesis at ambient conditions. Albeit the “π back-donation” process enables N2RR activity on transition metals with empty d-orbitals, given its dilemma in overcoming hydrogen evolution reaction (HER) competition, exploring p-block-element-based catalysts with relatively inferior HER activity is achievable for high selectivity. The challenge lies in designing rational structure to improve N2RR activity. Here, we synergistically integrate oxygen vacancy (VO) with hydroxyl on Bi4O5I2 (VO-Bi4O5I2-OH), which render this p-block-element-based material active to mimic “π back-donation” behavior because of sufficient vacant orbitals. In neutral media, the electrocatalytic N2RR performance of VO-Bi4O5I2-OH in terms of splendid faradic efficiency (32.4%) is superior to most of the prior reports using p-block-element-based catalysts. Our findings show a new strategy toward standout N2RR activity, which holds great potential in exploiting other p-block-element-based electrocatalysts. Producing ammonia through an economical, sustainable approach has a profound impact on underpinning global agriculture. Electrocatalytic N2 reduction reaction (N2RR) is emerging as an alternative technology for synthesizing NH3 at ambient conditions. The poor hydrogen evolution ability of p-block-element catalysts emerge as promising candidates to produce ammonia with high selectivity (faradic efficiency [FE]). Due to the absence of d-orbitals, nevertheless, N2 activation and protonation are difficult on p-block-element catalysts. Employing rational surface electronic structure modulation can induce sufficient vacant orbitals, which promote N2 reduction through mimicking the “π back-donation” process. A standout electrocatalytic N2RR performance in terms of NH3 rate (20.44 μg h?1 mg?1cat.) and high FE of 32.4% is achieved in neutral electrolyte. This work motivates in-depth study to shed light on the new chemistry of ambient N2RR not relying on Haber-Bosch. Mimicking “π back-donation” is proposed as a facile, feasible, and generalizable approach to boost electrocatalytic ammonia production from dinitrogen on p-block-element catalysts, which lack d-orbitals. Such behavior is realized by providing sufficient empty orbitals on the surface of Bi4O5I2. The integrated modification of oxygen vacancy with hydroxyl achieves the generation of empty orbitals to reduce the energy barrier for N2 protonation. The intriguing strategy that takes advantage of the electronic structure modulation endows this p-block-element catalyst with a relatively high ammonia synthesis of 20.44 μg h?1 mg?1cat. in neutral media at a high faradic efficiency of 32.4%.
Fabrication of an Fe-Doped SrTiO3 Photocatalyst with Enhanced Dinitrogen Photofixation Performance
Ying, Zihao,Chen, Shengtao,Peng, Tianyou,Li, Renjie,Zhang, Jing
, p. 2182 - 2192 (2019)
SrTiO3 as semiconducting photocatalyst has been extensively investigated due to its band edges meeting the thermodynamic requirements for water splitting, but a few attention has been concentrated on its application in the NH3 synthesis via N2 photofixation process. Herein, Fe-doped SrTiO3 (FexSr1–xTiO3) products (0 ≤ x ≤ 0.20) were synthesized via a hydrothermal process followed by calcination at 700 °C. All FexSr1–xTiO3 products (0.03 ≤ x ≤ 0.20) deliver an enhanced N2 fixation ability, and FexSr1–xTiO3 (x = 0.10) achieves the best NH3 production activity of 30.1 μmol g–1 h–1, which is 3.2-hold higher than that of SrTiO3 alone. Once the x value is higher than 0.10, FexSr1–xTiO3 will transform into composites containing Fe-doped SrTiO3 and α-Fe2O3, which acts as charge recombination sites, thus causes a decreased N2 fixation activity. Further investigations demonstrate that the surface Fe3+-doped sites can not only chemisorb and activate N2 molecules, but also promote the interfacial electron transfer from Fe-doped SrTiO3 to N2 molecules, and thus significantly improve the N2 fixation ability. The present Fe-doped SrTiO3 products exhibit characteristic features such as stable and efficient N2 fixation ability as well as simultaneous realization of N2 reduction and H2O oxidation without co-catalyst, which are of significance in artificial photosynthesis with H2O as electron and proton sources.
Isotopic Evidence for Direct Conversion of NO to NH3 in the Absence of O2 over V2O5/TiO2 and α-Cr2O3 Selective Catalytic Reduction Catalysts
Duffy, Bronwyn L.,Curry-Hyde, H. Edward,Cant, Noel W.,Nelson, Peter F.
, p. 1729 - 1732 (1993)
The products of the reaction between (15)NO and (14)NH3 over V2O5/TiO2 and α-Cr2O3 catalysts in the absence of oxygen have been determined by mass spectrometry and Fourier transform infrared spectroscopy.With both catalysts (14)N(15)N comprises approximat
Sodium Hexamethyldisilazide: Using 15N-29Si Scalar Coupling to Determine Aggregation and Solvation States
Woltornist, Ryan A.,Collum, David B.
, p. 6852 - 6855 (2020)
29Si NMR spectroscopy, the method of continuous variations, and density functional theory computations show that sodium hexamethyldisilazide (NaHMDS) is a disolvated dimer in toluene, a mixture of disolvated dimer and tetrasolvated monomer in THF/toluene, and exclusively monomer in neat THF. The dioxane-solvated NaHMDS only partially deaggregates to monomer even in neat dioxane. 15N-29Si coupling constants and 29Si chemical shifts show a high and dependable correlation with the aggregation state. Monitoring either chemical shift or coupling constant versus THF concentration even in the high-temperature, rapid-exchange limit affords the solvation numbers consistent with DFT computations. The preparation of 15N-labeled NaHMDS has been improved.
Dinitrogen activation by a penta-pyridyl molybdenum complex
Cha, Jeongmin,Kwon, Hyunchul,Lee, Eunsung,Song, Hayoung
, p. 12945 - 12949 (2020)
A new dinitrogen (N2) molybdenum(0) complex supported exclusively by pyridine ligands was synthesized. The X-ray crystal structure of the complex elucidated the activated nature of the N2 ligand, consistent with a low N-N IR stretching frequency. Natural bond orbital (NBO) analyses on this system confirmed a strong π-backdonation arising from the large p orbital character in molybdenum lone pairs. The protonation of the N2 ligand using decamethyl chromocene (CrCp?2) in the presence of lutidinium salt afforded 1.22 equivalents of ammonia (NH3).
Gerke, M.,Schatte, G.,Willner, H.
, p. 359 - 369 (1989)
Regulation of the electronic structure of perovskites to improve the electrocatalytic performance for the nitrogen-reduction reaction
Bao, Di,Jiao, Meng-Gai,Li, Kai,Shi, Miao-Miao,Wang, Jia-Zhi,Wen, Zi,Zhang, Yan
supporting information, p. 2819 - 2825 (2022/02/21)
Ammonia has received widespread attention as an indispensable chemical for humans and a potential energy source for a future low-carbon society. To meet the urgent requirements for a high output of synthetic ammonia by the electrocatalytic nitrogen reduction reaction (ENRR), the design of robust catalysts has become particularly important. Adjusting the charge and spin configuration of catalysts is a novel and effective way to optimize the ENRR barrier. We found that, through doping Co atoms, there was a correlation between the effective spin magnetic moment of the Co-LNO (Co-doped LaNiO3) catalyst and its catalytic performance for the ENRR. Uniquely, LaNi0.995Co0.005O3-δ with a high spin configuration was endowed with an excellent ENRR performance, including a high ammonia yield rate of 14.57 μg h-1 mg-1, an outstanding faradaic efficiency of 26.44%, and a remarkable energy efficiency of 21.35% (-0.1 V vs. the reversible hydrogen electrode). According to density functional theory calculations, we infer that Co-LNO provides Co with catalytically active sites and the accompanying oxygen vacancies to adjust the electronic structure and promote N2 adsorption and the first protonation to form ?NNH.
Amorphization engineered VSe2-: Xnanosheets with abundant Se-vacancies for enhanced N2electroreduction
Chu, Ke,Li, Qingqing,Liu, Yaping,Luo, Yaojing,Tian, Ye
supporting information, p. 1742 - 1749 (2022/02/02)
Electrochemical N2 fixation through the nitrogen reduction reaction (NRR) is a promising route for sustainable NH3 synthesis, while exploring high-performance NRR catalysts lies at the heart of achieving high-efficiency NRR electrocatalysis. Herein, we reported the structural regulation of VSe2 by amorphization engineering, which simultaneously triggered the enriched Se-vacancies. The developed amorphous VSe2-x nanosheets with abundant Se-vacancies (a-VSe2-x) delivered a much enhanced NRR activity with an NH3 yield of 65.7 μg h-1 mg-1 and a faradaic efficiency of 16.3% at -0.4 V, being 8.8- and 3.5-fold higher than those of their crystalline counterparts, respectively. Density functional theory computations combined with molecular dynamics simulations revealed that the amorphization-triggered Se-vacancies could induce the upraised d-band center of unsaturated V atoms, capable of promoting the binding of key ?N2/?NNH species to result in an energetically favorable NRR process. This journal is
