Hanyu Xu 1,Xuedan Song 1,*,Qing Zhang 1,Chang Yu 1,Jieshan Qiu 1,2,*1 Liaoning Key Lab for Energy Materials and Chemical Engineering,State Key Laboratory of Fine Chemicals,School of Chemical Engineering,Dalian Univers...Hanyu Xu 1,Xuedan Song 1,*,Qing Zhang 1,Chang Yu 1,Jieshan Qiu 1,2,*1 Liaoning Key Lab for Energy Materials and Chemical Engineering,State Key Laboratory of Fine Chemicals,School of Chemical Engineering,Dalian University of Technology,Dalian 116024,Liaoning Province,China.展开更多
The nitrogen-coordinated metal single-atom catalysts(M−N−C SACs)with an ultra-high metal loading synthetized by direct high-temperature pyrolysis have been widely reported.However,most of metal single atoms in these c...The nitrogen-coordinated metal single-atom catalysts(M−N−C SACs)with an ultra-high metal loading synthetized by direct high-temperature pyrolysis have been widely reported.However,most of metal single atoms in these catalysts were buried in the carbon matrix,resulting in a low metal utilization and inaccessibility for adsorption of reactants during the catalytic process.Herein,we reported a facile synthesis based on the hard-soft acid-base(HSAB)theory to fabricate Co single-atom catalysts with highly exposed metal atoms ligated to the external pyridinic-N sites of a nitrogen-doped carbon support.Benefiting from the highly accessible Co active sites,the prepared Co−N−C SAC exhibited a superior oxygen reduction reactivity comparable to that of the commercial Pt/C catalyst,showing a high turnover frequency(TOF)of 0.93 e^(−)·s^(-1)·site^(-1)at 0.85 V vs.RHE,far exceeding those of some representative SACs with a ultra-high metal content.This work provides a rational strategy to design and prepare M−N−C single-atom catalysts featured with high site-accessibility and site-density.展开更多
Platinum-ruthenium alloys(PtRu)represent state-of-the-art alkaline hydrogen oxidation reaction(HOR)catalysts,yet the atomic-scale origin of their superiority over pure Pt remains incompletely understood.Here,we employ...Platinum-ruthenium alloys(PtRu)represent state-of-the-art alkaline hydrogen oxidation reaction(HOR)catalysts,yet the atomic-scale origin of their superiority over pure Pt remains incompletely understood.Here,we employ density functional theory calculations,ab initio molecular dynamics simulations,and microkinetic modeling on Pt(111)and PtRu(111)surfaces to systematically investigate the key factors,including active sites distribution,species adsorption,and solvent reorganization,that affect the HOR activity and decouple their contributions.The results reveal that while the moderate hydrogen binding energy and improved hydroxyl(OH)species adsorption both contribute to the enhanced activity,the dominant factor is the substantial reduction in solvent reorganization energy on the PtRu(111).This is facilitated by the spatial separation of active sites:Pt atoms preferentially stabilize adsorbed hydrogen,while Ru atoms strongly bind OH and interfacial water molecules.This configuration increases the probability of hydrogen interacting with OH/water and enhances the fraction of"H-up"water molecules,forming a well-organized hydrogen bond network within the electric double layer.The dynamically compatible interfacial water structure and HOR coordination promote H desorption and proton transfer in the Volmer step,thereby accelerating the HOR kinetics.展开更多
With the development of renewable energy,electrochemical carbon dioxide reduction reaction(CO_(2)RR)has become a potential solution for achieving carbon neutrality.However,until now,due to issues with salt precipitate...With the development of renewable energy,electrochemical carbon dioxide reduction reaction(CO_(2)RR)has become a potential solution for achieving carbon neutrality.However,until now,due to issues with salt precipitate and regeneration of the electrolyte,this technology faces challenges such as difficulty in maintaining long-term stable operation and excessive costs.The pure water CO_(2)electrolyzers are believed to be the ultimate solution to eliminate the salt depreciation and electrolyte issues.This study develops an in-situ method tailored for CO_(2)reduction in pure water.By employing distribution of relaxation times(DRT)analysis and in-situ electrochemical active surface area(ECSA)measurements,we carried out a comprehensive investigation into the mass transport and electrochemical active surface area of gas diffusion electrodes(GDE)under pure water conditions.The maximum 89%CO selectivity and high selectivity(>80%)in the range of 0-300 mA/cm^(2)were achieved using commercial Ag nanoparticles by rational design of catalyst layer.We found that ionomers influence the CO_(2)electrolyzers performance via affecting local pH,GDE-membrane interface,and CO_(2)transport,while catalyst loading mainly influences the active area and CO_(2)transport.This work provides benchmark and insights for future pure water CO_(2)electrolyzers development.展开更多
The metal oxide promoter decisively influences the overall performance of Fe catalysts in the direct hydrogenation of CO_(2)to C_(5+)hydrocarbons.However,the roles of metal oxide promoter for Fe catalysts,particularly...The metal oxide promoter decisively influences the overall performance of Fe catalysts in the direct hydrogenation of CO_(2)to C_(5+)hydrocarbons.However,the roles of metal oxide promoter for Fe catalysts,particularly ZrO_(2),have rarely been investigated.To plug this knowledge gap,a new Fe catalyst promoted with Na and partially reduced ZrO_(x)(Na-FeZrO_(x-9))was developed in this study;the catalyst helped produce C_(5+)hydrocarbons in remarkably high yield(26.3%at 360℃).In contrast to ZrO_(x)-free Fe-oxide,NaFeZrO_(x)-9 exhibited long-term stability for CO_(2)hydrogenation(750 h on-stream).The findings revealed multiple roles of ZrO_(x).Notably,ZrO_(x)decorated the Fe-oxide particles after calcination,thereby suppressing excess particle aggregation during the reaction,and acted as a"coke remover"to eliminate the carbon deposited on the catalyst surface.Additionally,oxygen vacancy(O_(v))sites in ZrO_(x)and electron transfer from ZrO_(x)to Fe sites facilitated the adsorption of CO_(2)at the Zr-Fe interface.展开更多
Metal(oxide)-zeolite bifunctional catalysts have been the subject of considerable attention from researchers in both academic and industry,due to their superior activity and stability in various heterogeneous catalyti...Metal(oxide)-zeolite bifunctional catalysts have been the subject of considerable attention from researchers in both academic and industry,due to their superior activity and stability in various heterogeneous catalytic processes[1–3].Based on the different metal loading sites,these bifunctional catalysts can be categorized as follows:(a)metal species loaded on the outer surface of zeolite crystals,(b)metal species encapsulated within the channels or cavities of zeolites,and(c)metal species incorporated into the zeolite framework(Fig.1).Metal species in type(b)and(c)samples are stabilized by the zeolite frameworks,resulting in excellent thermal and hydrothermal stability during catalytic reactions,especially under harsh conditions,as well as unique shape-selectivity.However,the complex synthesis procedures make large-scale preparation of these catalysts impractical.In contrast,a type(a)sample can be achieved via the simple impregnation;nevertheless,migration of metal species and their aggregation into larger particles often occur during the calcination and reduction processes.展开更多
High-loading Pt/C catalysts play an important role in the fabrication of membrane electrode assemblies with thin catalytic layer,which enhance mass transport and maintain the balance of water and heat.Unfortunately,as...High-loading Pt/C catalysts play an important role in the fabrication of membrane electrode assemblies with thin catalytic layer,which enhance mass transport and maintain the balance of water and heat.Unfortunately,as the loading increases,the agglomeration and growth of Pt nanoparticles(NPs)occur,causing unsatisfactory performance.Here,we present an efficient method for preparing of highly dispersed and small-sized Pt/C catalysts with Pt loadings varying from 39.01 wt%to 66.48 wt%through the high-temperature shock technique.The high density and ultrafine(~2.5 nm)Pt NPs are successfully anchored onto Vulcan XC-72R carbon black without the use of additional capping agents or surfactants.The modified carbon supports enhance the affinity for Pt precursors,contributing to loading efficiencies of 95%or more,while also providing abundant sites for the nucleation and fixation of Pt NPs,thus preventing agglomeration.In the context of the hydrogen evolution reaction in acidic media,the as-synthesized high-loading Pt/C catalysts show remarkable activity and stability,outperforming the state-of-the-art commercial Pt/C.This is mainly because the combined effects of ultrasmall and uniform Pt NPs,optimized electronic structure of Pt site,superhydrophilicity and effective anchoring of Pt NPs.The polymer electrolyte membrane electrolyzer integrated with Pt60/OX72R and commercial IrO2 reaches 1 A cm^(-2)at 1.77 V and operates stably for 120 hours with a negligible voltage decay.This new strategy is fast,scalable and cost-effective for large-scale production of metal-supported catalysts,especially for the high-loading ones.展开更多
A core shell structured C@MoxTi1-xO2-δnanocrystal with a functionalized interface(C@MTNC-FI)was fabricated via the hydrothermal method with subsequent annealing derived from tetrabutyl orthotitanate.The formation of ...A core shell structured C@MoxTi1-xO2-δnanocrystal with a functionalized interface(C@MTNC-FI)was fabricated via the hydrothermal method with subsequent annealing derived from tetrabutyl orthotitanate.The formation of anatase TiO2 was inhibited by the simultaneous presence of the hydrothermal etching/regrowth process,infiltration of Mo dopants and carbon coating,which endows the C@MTNC-FI with an ultrafine crystalline architecture that has a Mo-functionalized interface and carbon-coated shell.Pt Ru nanoparticles(NPs)were supported on C@MTNC-FI by employing a microwave-assisted polyol process(MAPP).The obtained Pt Ru/C@MTNC-FI catalyst has 2.68 times higher mass activity towards methanol electrooxidation than that of the un-functionalized catalyst(Pt Ru/C@TNC)and 1.65 times higher mass activity than that of Pt Ru/C catalyst with over 25%increase in durability.The improved catalytic performance is due to several aspects including ultrafine crystals of TiO2 with abundant grain boundaries,Mofunctionalized interface with enhanced electron interactions,and core shell architecture with excellent electrical transport properties.This work suggests the potential application of an interface-functionalized crystalline material as a sustainable and clean energy solution.展开更多
Carbon-supported PtPdRuIr, Pd@PtRuIr, PtPd@PtRuIr, and PtPdRu@PtRuIr catalysts were prepared by a colloidal method and their catalytic activities to the methanol oxidation reaction in the acidic media were extensively...Carbon-supported PtPdRuIr, Pd@PtRuIr, PtPd@PtRuIr, and PtPdRu@PtRuIr catalysts were prepared by a colloidal method and their catalytic activities to the methanol oxidation reaction in the acidic media were extensively investigated at room temperature. The catalysts were characterized by transmission electron microscopy and X-ray diffraction techniques, and their electrochemical behavior was evaluated by the cyclic voltammetry. The PtPdRu@PtRuIr/C catalyst is found to yield much higher electrocatalytic activity than the other ones and the commercial catalyst. For example, the Pt metal mass-specific activity of this PtPdRu@PtRuIr/C（Pt content 10 wt%,1.7 mAácm-2ámg-1） electrocatalyst is ＊3-fold higher than that of the commercial JM 40 % Pt/C（0.6 mAácm-2ámg-1）electrocatalysts, and the If/Ib ratio of PtPdRu@PtRuIr/C is1.6, which is higher than that of the JM 40 % Pt/C（0.9）. The improvement may result from the high dispersion of the active metal catalyst and the synergistic effect between the PtRuIr and PtPdRu layers. It is thus concluded that the pseudo-core-shell structure could significantly improve the methanol electro-oxidation activity and CO tolerance of the electrocatalyst.展开更多
[目的]为进一步拓展单原子催化剂在亚硝酸盐还原制氨领域的应用,提出了一种铁-氮-碳(Fe-N-C)单原子催化剂电催化亚硝酸盐还原制氨的新体系.[方法]以二氧化硅为硬模板,2,6-二氨基吡啶为碳氮前驱体,硝酸铁为金属盐,通过“热解-刻蚀”策略...[目的]为进一步拓展单原子催化剂在亚硝酸盐还原制氨领域的应用,提出了一种铁-氮-碳(Fe-N-C)单原子催化剂电催化亚硝酸盐还原制氨的新体系.[方法]以二氧化硅为硬模板,2,6-二氨基吡啶为碳氮前驱体,硝酸铁为金属盐,通过“热解-刻蚀”策略制备了Fe-N-C单原子催化剂,并将其应用于亚硝酸盐制氨反应.[结果]多种结构表征结果显示,Fe-N-C催化剂表面的Fe物种呈现高度分散特征并以单原子形式存在.此外,Fe物种的化学环境主要是+2和+3价混合态,且通过与4个吡啶氮配位而稳定存在,即Fe-N-C催化剂的金属中心微观配位环境为Fe-N4结构.与纯氮碳(N-C)载体相比,本研究制备的Fe-N-C催化剂具有优异的亚硝酸盐还原性能,不仅表现出更高的起始还原电位(0 V vs可逆氢电极),具有接近100%的产氨法拉第效率和高的氨产率[8.4 mg/(h·cm^(2))],并且在连续20次催化循环测试中显示出优异的催化稳定性.[结论]本研究制备的Fe-N-C单原子催化剂对亚硝酸盐还原制氨具有优异的电催化活性,其高活性可能来源于对NO_(2)^(-)的显著吸附,并进一步促进活性氢参与脱氧加氢过程.该Fe-N-C单原子催化亚硝酸盐还原体系可为后续合成氨的活性中心设计提供指导方向.展开更多
Extremely small PtRu/C nanocatalysts were prepared via a carbonyl route. A thorough in situ reduction X-ray structural characterization of these catalysts was performed. After synthesis and storage under ambient condi...Extremely small PtRu/C nanocatalysts were prepared via a carbonyl route. A thorough in situ reduction X-ray structural characterization of these catalysts was performed. After synthesis and storage under ambient condi- tions, the diffraction patterns of PtRu/C catalysts were seriously modified, indicating the surface oxide formation. In the reduced state, the particle size is around 2 nm. The observed relative fluctuations of lattice constants are 3%, which is far too large to be explained by a compositional fluctuation. Their origin is attributed to strong but isotropic strains and is related to the alloy formation. The annealing experiments show all the catalysts present an exceptional thermal stability when annealed in inert ambient, especially that of the Pt1Ru1/C catalyst. Besides, it is interesting to note that there is no thermal expansion evidence from the patterns.展开更多
文摘Hanyu Xu 1,Xuedan Song 1,*,Qing Zhang 1,Chang Yu 1,Jieshan Qiu 1,2,*1 Liaoning Key Lab for Energy Materials and Chemical Engineering,State Key Laboratory of Fine Chemicals,School of Chemical Engineering,Dalian University of Technology,Dalian 116024,Liaoning Province,China.
基金supported by Shanxi Province Science Foundation for Youths(202203021212300)Taiyuan University of Science and Technology Scientific Research Initial Funding(20212064)Outstanding Doctoral Award Fund in Shanxi Province(20222060).
文摘The nitrogen-coordinated metal single-atom catalysts(M−N−C SACs)with an ultra-high metal loading synthetized by direct high-temperature pyrolysis have been widely reported.However,most of metal single atoms in these catalysts were buried in the carbon matrix,resulting in a low metal utilization and inaccessibility for adsorption of reactants during the catalytic process.Herein,we reported a facile synthesis based on the hard-soft acid-base(HSAB)theory to fabricate Co single-atom catalysts with highly exposed metal atoms ligated to the external pyridinic-N sites of a nitrogen-doped carbon support.Benefiting from the highly accessible Co active sites,the prepared Co−N−C SAC exhibited a superior oxygen reduction reactivity comparable to that of the commercial Pt/C catalyst,showing a high turnover frequency(TOF)of 0.93 e^(−)·s^(-1)·site^(-1)at 0.85 V vs.RHE,far exceeding those of some representative SACs with a ultra-high metal content.This work provides a rational strategy to design and prepare M−N−C single-atom catalysts featured with high site-accessibility and site-density.
文摘Platinum-ruthenium alloys(PtRu)represent state-of-the-art alkaline hydrogen oxidation reaction(HOR)catalysts,yet the atomic-scale origin of their superiority over pure Pt remains incompletely understood.Here,we employ density functional theory calculations,ab initio molecular dynamics simulations,and microkinetic modeling on Pt(111)and PtRu(111)surfaces to systematically investigate the key factors,including active sites distribution,species adsorption,and solvent reorganization,that affect the HOR activity and decouple their contributions.The results reveal that while the moderate hydrogen binding energy and improved hydroxyl(OH)species adsorption both contribute to the enhanced activity,the dominant factor is the substantial reduction in solvent reorganization energy on the PtRu(111).This is facilitated by the spatial separation of active sites:Pt atoms preferentially stabilize adsorbed hydrogen,while Ru atoms strongly bind OH and interfacial water molecules.This configuration increases the probability of hydrogen interacting with OH/water and enhances the fraction of"H-up"water molecules,forming a well-organized hydrogen bond network within the electric double layer.The dynamically compatible interfacial water structure and HOR coordination promote H desorption and proton transfer in the Volmer step,thereby accelerating the HOR kinetics.
基金supported by the National Natural Science Foundation of China(No.52394204)by the Shanghai Municipal Science and Technology Major Project。
文摘With the development of renewable energy,electrochemical carbon dioxide reduction reaction(CO_(2)RR)has become a potential solution for achieving carbon neutrality.However,until now,due to issues with salt precipitate and regeneration of the electrolyte,this technology faces challenges such as difficulty in maintaining long-term stable operation and excessive costs.The pure water CO_(2)electrolyzers are believed to be the ultimate solution to eliminate the salt depreciation and electrolyte issues.This study develops an in-situ method tailored for CO_(2)reduction in pure water.By employing distribution of relaxation times(DRT)analysis and in-situ electrochemical active surface area(ECSA)measurements,we carried out a comprehensive investigation into the mass transport and electrochemical active surface area of gas diffusion electrodes(GDE)under pure water conditions.The maximum 89%CO selectivity and high selectivity(>80%)in the range of 0-300 mA/cm^(2)were achieved using commercial Ag nanoparticles by rational design of catalyst layer.We found that ionomers influence the CO_(2)electrolyzers performance via affecting local pH,GDE-membrane interface,and CO_(2)transport,while catalyst loading mainly influences the active area and CO_(2)transport.This work provides benchmark and insights for future pure water CO_(2)electrolyzers development.
基金financial support from the National Research Council of Science&Technology(NST)grant funded by the Ministry of Science and ICT,Republic of Korea(CAP21012-100)the Korea Institute of Energy Technology Evaluation and Planning(KETEP),under the Ministry of Trade,Industry&Energy(MOTIE),Republic of Korea(20224C10300010)the KETEP grant funded by the MOTIE(20224000000440,Sector coupling energy industry advancement manpower training program)。
文摘The metal oxide promoter decisively influences the overall performance of Fe catalysts in the direct hydrogenation of CO_(2)to C_(5+)hydrocarbons.However,the roles of metal oxide promoter for Fe catalysts,particularly ZrO_(2),have rarely been investigated.To plug this knowledge gap,a new Fe catalyst promoted with Na and partially reduced ZrO_(x)(Na-FeZrO_(x-9))was developed in this study;the catalyst helped produce C_(5+)hydrocarbons in remarkably high yield(26.3%at 360℃).In contrast to ZrO_(x)-free Fe-oxide,NaFeZrO_(x)-9 exhibited long-term stability for CO_(2)hydrogenation(750 h on-stream).The findings revealed multiple roles of ZrO_(x).Notably,ZrO_(x)decorated the Fe-oxide particles after calcination,thereby suppressing excess particle aggregation during the reaction,and acted as a"coke remover"to eliminate the carbon deposited on the catalyst surface.Additionally,oxygen vacancy(O_(v))sites in ZrO_(x)and electron transfer from ZrO_(x)to Fe sites facilitated the adsorption of CO_(2)at the Zr-Fe interface.
基金financially supported by the National Key R&D Program of China(2024YFE0101100)the National Natural Science Foundation of China(22475112,22305132,22305155)+1 种基金the China Postdoctoral Science Foundation(2023M732323)the Postdoctoral Fellowship Program of CPSF(GZC20231679).
文摘Metal(oxide)-zeolite bifunctional catalysts have been the subject of considerable attention from researchers in both academic and industry,due to their superior activity and stability in various heterogeneous catalytic processes[1–3].Based on the different metal loading sites,these bifunctional catalysts can be categorized as follows:(a)metal species loaded on the outer surface of zeolite crystals,(b)metal species encapsulated within the channels or cavities of zeolites,and(c)metal species incorporated into the zeolite framework(Fig.1).Metal species in type(b)and(c)samples are stabilized by the zeolite frameworks,resulting in excellent thermal and hydrothermal stability during catalytic reactions,especially under harsh conditions,as well as unique shape-selectivity.However,the complex synthesis procedures make large-scale preparation of these catalysts impractical.In contrast,a type(a)sample can be achieved via the simple impregnation;nevertheless,migration of metal species and their aggregation into larger particles often occur during the calcination and reduction processes.
文摘High-loading Pt/C catalysts play an important role in the fabrication of membrane electrode assemblies with thin catalytic layer,which enhance mass transport and maintain the balance of water and heat.Unfortunately,as the loading increases,the agglomeration and growth of Pt nanoparticles(NPs)occur,causing unsatisfactory performance.Here,we present an efficient method for preparing of highly dispersed and small-sized Pt/C catalysts with Pt loadings varying from 39.01 wt%to 66.48 wt%through the high-temperature shock technique.The high density and ultrafine(~2.5 nm)Pt NPs are successfully anchored onto Vulcan XC-72R carbon black without the use of additional capping agents or surfactants.The modified carbon supports enhance the affinity for Pt precursors,contributing to loading efficiencies of 95%or more,while also providing abundant sites for the nucleation and fixation of Pt NPs,thus preventing agglomeration.In the context of the hydrogen evolution reaction in acidic media,the as-synthesized high-loading Pt/C catalysts show remarkable activity and stability,outperforming the state-of-the-art commercial Pt/C.This is mainly because the combined effects of ultrasmall and uniform Pt NPs,optimized electronic structure of Pt site,superhydrophilicity and effective anchoring of Pt NPs.The polymer electrolyte membrane electrolyzer integrated with Pt60/OX72R and commercial IrO2 reaches 1 A cm^(-2)at 1.77 V and operates stably for 120 hours with a negligible voltage decay.This new strategy is fast,scalable and cost-effective for large-scale production of metal-supported catalysts,especially for the high-loading ones.
基金the National Natural Science Foundation of China (Grant Nos. 21273058, 21673064, 51802059 and 21503059)China Postdoctoral Science Foundation (Grant Nos. 2018M631938, 2018T110307 and 2017M621284)+1 种基金Heilongjiang Postdoctoral Fund (LBH-Z17074)Fundamental Research Funds for the Central Universities (Grant No. HIT. NSRIF. 2019040 and 2019041)
文摘A core shell structured C@MoxTi1-xO2-δnanocrystal with a functionalized interface(C@MTNC-FI)was fabricated via the hydrothermal method with subsequent annealing derived from tetrabutyl orthotitanate.The formation of anatase TiO2 was inhibited by the simultaneous presence of the hydrothermal etching/regrowth process,infiltration of Mo dopants and carbon coating,which endows the C@MTNC-FI with an ultrafine crystalline architecture that has a Mo-functionalized interface and carbon-coated shell.Pt Ru nanoparticles(NPs)were supported on C@MTNC-FI by employing a microwave-assisted polyol process(MAPP).The obtained Pt Ru/C@MTNC-FI catalyst has 2.68 times higher mass activity towards methanol electrooxidation than that of the un-functionalized catalyst(Pt Ru/C@TNC)and 1.65 times higher mass activity than that of Pt Ru/C catalyst with over 25%increase in durability.The improved catalytic performance is due to several aspects including ultrafine crystals of TiO2 with abundant grain boundaries,Mofunctionalized interface with enhanced electron interactions,and core shell architecture with excellent electrical transport properties.This work suggests the potential application of an interface-functionalized crystalline material as a sustainable and clean energy solution.
基金financially supported by the National Natural Scientific Foundation of China (Nos. 20673040 and20876062)Guangdong Provincial Scientific Foundation (Nos. 36055 and S2012040007383)the Key Laboratory of Fuel Cell Technology of Guangdong Province (No. 201112)
文摘Carbon-supported PtPdRuIr, Pd@PtRuIr, PtPd@PtRuIr, and PtPdRu@PtRuIr catalysts were prepared by a colloidal method and their catalytic activities to the methanol oxidation reaction in the acidic media were extensively investigated at room temperature. The catalysts were characterized by transmission electron microscopy and X-ray diffraction techniques, and their electrochemical behavior was evaluated by the cyclic voltammetry. The PtPdRu@PtRuIr/C catalyst is found to yield much higher electrocatalytic activity than the other ones and the commercial catalyst. For example, the Pt metal mass-specific activity of this PtPdRu@PtRuIr/C（Pt content 10 wt%,1.7 mAácm-2ámg-1） electrocatalyst is ＊3-fold higher than that of the commercial JM 40 % Pt/C（0.6 mAácm-2ámg-1）electrocatalysts, and the If/Ib ratio of PtPdRu@PtRuIr/C is1.6, which is higher than that of the JM 40 % Pt/C（0.9）. The improvement may result from the high dispersion of the active metal catalyst and the synergistic effect between the PtRuIr and PtPdRu layers. It is thus concluded that the pseudo-core-shell structure could significantly improve the methanol electro-oxidation activity and CO tolerance of the electrocatalyst.
文摘[目的]为进一步拓展单原子催化剂在亚硝酸盐还原制氨领域的应用,提出了一种铁-氮-碳(Fe-N-C)单原子催化剂电催化亚硝酸盐还原制氨的新体系.[方法]以二氧化硅为硬模板,2,6-二氨基吡啶为碳氮前驱体,硝酸铁为金属盐,通过“热解-刻蚀”策略制备了Fe-N-C单原子催化剂,并将其应用于亚硝酸盐制氨反应.[结果]多种结构表征结果显示,Fe-N-C催化剂表面的Fe物种呈现高度分散特征并以单原子形式存在.此外,Fe物种的化学环境主要是+2和+3价混合态,且通过与4个吡啶氮配位而稳定存在,即Fe-N-C催化剂的金属中心微观配位环境为Fe-N4结构.与纯氮碳(N-C)载体相比,本研究制备的Fe-N-C催化剂具有优异的亚硝酸盐还原性能,不仅表现出更高的起始还原电位(0 V vs可逆氢电极),具有接近100%的产氨法拉第效率和高的氨产率[8.4 mg/(h·cm^(2))],并且在连续20次催化循环测试中显示出优异的催化稳定性.[结论]本研究制备的Fe-N-C单原子催化剂对亚硝酸盐还原制氨具有优异的电催化活性,其高活性可能来源于对NO_(2)^(-)的显著吸附,并进一步促进活性氢参与脱氧加氢过程.该Fe-N-C单原子催化亚硝酸盐还原体系可为后续合成氨的活性中心设计提供指导方向.
基金Supported by the National Natural Science Foundation of China(No.21073219)the Youth’s Innovation Fund of the Shanghai Institute of Microsystem and Information Technology,China(No.2010)
文摘Extremely small PtRu/C nanocatalysts were prepared via a carbonyl route. A thorough in situ reduction X-ray structural characterization of these catalysts was performed. After synthesis and storage under ambient condi- tions, the diffraction patterns of PtRu/C catalysts were seriously modified, indicating the surface oxide formation. In the reduced state, the particle size is around 2 nm. The observed relative fluctuations of lattice constants are 3%, which is far too large to be explained by a compositional fluctuation. Their origin is attributed to strong but isotropic strains and is related to the alloy formation. The annealing experiments show all the catalysts present an exceptional thermal stability when annealed in inert ambient, especially that of the Pt1Ru1/C catalyst. Besides, it is interesting to note that there is no thermal expansion evidence from the patterns.
