Fe-N-C catalysts,as promising non-precious metal alternatives for the oxygen reduction reaction(ORR),still suffer from severe mass transport limitations in proton exchange membrane fuel cells(PEMFCs)due to water flood...Fe-N-C catalysts,as promising non-precious metal alternatives for the oxygen reduction reaction(ORR),still suffer from severe mass transport limitations in proton exchange membrane fuel cells(PEMFCs)due to water flooding of active sites embedded in micropores.Although pore engineering through a selected template is a general strategy,the structural features of an ideal template,particularly those governing the exposure of active sites and thus affecting mass transport,remain elusive.Here,we demonstrate that low-porosity carbon templates maximize the ratio of active sites distributed at or near the surface,thereby enhancing their exposure and accessibility while reducing mass transport resistance during the ORR process.The C_(lp-1)@PPy and C_(lp-2)@PPy(PPy=polypyrrole)catalysts,derived from low-porosity carbon templates,achieve peak power densities of 0.96 and 1.03 W·cm^(-2) under H_(2)/O_(2)and 0.50 and 0.52 W·cm^(-2) under H_(2)/air,demonstrating excellent performance in PEMFC tests.Structural and electrochemical characterizations reveal that the enhanced surface exposure of active sites effectively mitigates mass transport resistance during the ORR,thereby offering a general design principle for overcoming mass transport limitations in Fe-N-C catalysts for PEMFC applications.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
The remediation of nitroaromatic-contaminated water systems remains a critical environmental challenge,creating the urgent need for cost-effective,non-precious metal catalysts to increase wastewater biodegradability.I...The remediation of nitroaromatic-contaminated water systems remains a critical environmental challenge,creating the urgent need for cost-effective,non-precious metal catalysts to increase wastewater biodegradability.In this study,we present an Fe/N-functionalized three-dimensional porous carbon(Fe-N-C)catalyst synthesized via a straightforward pyrolysis approach that enables efficient nitrobenzene(NB)degradation via electrochemical and chemical reduction pathways.The hightemperature pyrolysis process facilitates the iron-catalyzed reconstruction of the carbon matrix,resulting in a hierarchically porous structure with increased graphitization and uniformly distributed macrocyclic Fe-N_(4) coordination sites.These structural features give the Fe-N-C catalyst exceptional electron transfer kinetics,catalytic activity,and pH adaptability,surpassing conventional graphite(GR)and nitrogen-doped carbons(NPCs)in NB reduction.Systematic evaluation of the electrochemical reduction performance revealed that the Fe-N-C electrode achieved the highest NB removal efficiency.To further assess the versatility of the catalyst,a functionalized Fe-N-C/zero-valent iron(ZVI)composite was engineered by integrating Fe-N-C as a catalytic layer onto the reductant ZVI.Compared with ZVI alone,this composite markedly increased the NB reduction efficiency.These findings provide valuable insights into the electrochemical reduction process of Fe-N-C and new directions for the rational design of efficient nitrobenzene reduction systems.展开更多
以苯胺为原料,二氧化硅球为硬模板,采用原位聚合法制备出具有多孔结构的氮掺杂碳球,然后以三氯化铁为铁源,利用沉淀法制备出球状多孔Fe-N-C复合催化剂.通过SEM、TEM、EDS等分析手段对Fe-N-C的形貌结构及组成进行了表征,使用旋转圆盘电...以苯胺为原料,二氧化硅球为硬模板,采用原位聚合法制备出具有多孔结构的氮掺杂碳球,然后以三氯化铁为铁源,利用沉淀法制备出球状多孔Fe-N-C复合催化剂.通过SEM、TEM、EDS等分析手段对Fe-N-C的形貌结构及组成进行了表征,使用旋转圆盘电极测试了其在碱性条件下对氧还原反应的催化活性.结果表明,其起始电位(0.961 V vs RHE)与半波电位(0.835 V vs RHE)与商业化Pt/C相近,经过7 000 s后,Fe-N-C仍保持93.53%的相对电流,显示出优异的氧还原催化稳定性.展开更多
Proton exchange membrane fuel cells(PEMFC)have attracted much attention because of their high energy conversion efficiency,high power density and zero emission of pollutants.However,the high cost of the cathode platin...Proton exchange membrane fuel cells(PEMFC)have attracted much attention because of their high energy conversion efficiency,high power density and zero emission of pollutants.However,the high cost of the cathode platinum group metal(PGM)catalysts creates a barrier for the large-scale application of PEMFC.Tremendous efforts have been devoted to the development of low-cost PGM-free catalysts,especially the Fe-N-C catalysts,to replace the expensive PGM catalysts.However,the characterization methods and evaluation standards of the catalysts varies,which is not conducive to the comparison of PGM-free catalysts.U.S.Department of energy(DOE)is the only authority that specifies the testing standards and activity targets for PGM-free catalysts.In this review,the major breakthroughs of Fe-N-C catalysts are outlined with the reference of DOE standards and targets.The preparation and characteristics of these highly active Fe-N-C catalysts are briefly introduced.Moreover,the efforts on improving the mass transfer and the durability issue of Fe-N-C fuel cell are discussed.Finally,the prospective directions concerning the comprehensive evaluation of the Fe-N-C catalysts are proposed.展开更多
Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the ac...Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the active site hosts, its hostility to electron/mass transfer could lead to the incomplete fulfillment of the catalytic activity. Besides, the formation of inactive metallic Fe particles during the conventional catalyst synthesis could also decrease the active site density and complicate the identification of real active site. Herein, we developed a facial hydrogen etching methodology to yield single site Fe-N-C catalysts featured with micro/mesoporous hierarchical structure. The hydrogen concentration in pyrolysis process was designated to effectively regulate the pore structure and active site density of the resulted catalysts.The optimized sample achieves excellent ORR catalytic performance with an ultralow H2O2 yield(1%)and superb stability over 10,000 cycles. Our finding provides new thoughts for the rational design of hierarchically porous carbon-based materials and highly promising non-precious metal ORR catalysts.展开更多
Single-atom catalysts(SACs) with nitrogen-coordinated nonprecious metal sites have exhibited inimitable advantages in electrocatalysis.However,a large room for improving their activity and durability remains.Herein,we...Single-atom catalysts(SACs) with nitrogen-coordinated nonprecious metal sites have exhibited inimitable advantages in electrocatalysis.However,a large room for improving their activity and durability remains.Herein,we construct atomically dispersed Fe sites in N-doped carbon supports by secondary-atom-doped strategy.Upon the secondary doping,the density and coordination environment of active sites can be efficiently tuned,enabling the simultaneous improvement in the number and reactivity of the active site.Besides,structure optimizations in terms of the enlarged surface area and improved hydrophilicity can be achieved simultaneously.Due to the beneficial microstructure and abundant highly active FeN_5 moieties resulting from the secondary doping,the resultant catalyst exhibits an admirable half-wave potential of 0.81 V versus 0.83 V for Pt/C and much better stability than Pt/C in acidic media.This work would offer a general strategy for the design and preparation of highly active SACs for electrochemical energy devices.展开更多
基金the National Key R&D Program of China(No.2024YFA1509500)the National Natural Science Foundation of China(No.22479010)+5 种基金the financial support from the Chongqing Municipal Natural Science Foundation(No.CSTB2024NSCQJQX0034)Shenzhen Science and Technology Program(No.KJZD20240903101359020)the financial support from the National Natural Science Foundation of China(No.22372004)the support from the Experimental Center of Advanced Materials of the Beijing Institute of Technologythe technical support from Biological and Medical Engineering Core Facilities of Beijing Institute of Technologythe Analysis and Testing Center of Beijing Institute of Technology.
文摘Fe-N-C catalysts,as promising non-precious metal alternatives for the oxygen reduction reaction(ORR),still suffer from severe mass transport limitations in proton exchange membrane fuel cells(PEMFCs)due to water flooding of active sites embedded in micropores.Although pore engineering through a selected template is a general strategy,the structural features of an ideal template,particularly those governing the exposure of active sites and thus affecting mass transport,remain elusive.Here,we demonstrate that low-porosity carbon templates maximize the ratio of active sites distributed at or near the surface,thereby enhancing their exposure and accessibility while reducing mass transport resistance during the ORR process.The C_(lp-1)@PPy and C_(lp-2)@PPy(PPy=polypyrrole)catalysts,derived from low-porosity carbon templates,achieve peak power densities of 0.96 and 1.03 W·cm^(-2) under H_(2)/O_(2)and 0.50 and 0.52 W·cm^(-2) under H_(2)/air,demonstrating excellent performance in PEMFC tests.Structural and electrochemical characterizations reveal that the enhanced surface exposure of active sites effectively mitigates mass transport resistance during the ORR,thereby offering a general design principle for overcoming mass transport limitations in Fe-N-C catalysts for PEMFC applications.
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financial support from the National Natural Science Foundation of China(Nos.22178003,22478427,and 22438001)financial support from Science Foundation of China University of Petroleum,Beijing(Nos.2462023YJRC022 and 2462023BJRC006).
文摘The remediation of nitroaromatic-contaminated water systems remains a critical environmental challenge,creating the urgent need for cost-effective,non-precious metal catalysts to increase wastewater biodegradability.In this study,we present an Fe/N-functionalized three-dimensional porous carbon(Fe-N-C)catalyst synthesized via a straightforward pyrolysis approach that enables efficient nitrobenzene(NB)degradation via electrochemical and chemical reduction pathways.The hightemperature pyrolysis process facilitates the iron-catalyzed reconstruction of the carbon matrix,resulting in a hierarchically porous structure with increased graphitization and uniformly distributed macrocyclic Fe-N_(4) coordination sites.These structural features give the Fe-N-C catalyst exceptional electron transfer kinetics,catalytic activity,and pH adaptability,surpassing conventional graphite(GR)and nitrogen-doped carbons(NPCs)in NB reduction.Systematic evaluation of the electrochemical reduction performance revealed that the Fe-N-C electrode achieved the highest NB removal efficiency.To further assess the versatility of the catalyst,a functionalized Fe-N-C/zero-valent iron(ZVI)composite was engineered by integrating Fe-N-C as a catalytic layer onto the reductant ZVI.Compared with ZVI alone,this composite markedly increased the NB reduction efficiency.These findings provide valuable insights into the electrochemical reduction process of Fe-N-C and new directions for the rational design of efficient nitrobenzene reduction systems.
文摘Fe-N-C材料是目前非常有潜力的一类非贵金属氧还原电极催化剂。本论文分别以导电碳黑(HG-1F)、苯胺、Fe Cl3为碳载体、含氮前驱体、铁前驱体,依次经过聚合、热处理和酸处理获得了多孔Fe-N-C材料。电化学测试结果表明,多孔Fe-N-C材料在0.1 M KOH中催化氧还原反应(ORR)的活性随酸处理时间呈火山型变化,其中酸处理4 h的样品对ORR具有较高的催化活性,促使ORR主要以4电子反应途径进行。
文摘以苯胺为原料,二氧化硅球为硬模板,采用原位聚合法制备出具有多孔结构的氮掺杂碳球,然后以三氯化铁为铁源,利用沉淀法制备出球状多孔Fe-N-C复合催化剂.通过SEM、TEM、EDS等分析手段对Fe-N-C的形貌结构及组成进行了表征,使用旋转圆盘电极测试了其在碱性条件下对氧还原反应的催化活性.结果表明,其起始电位(0.961 V vs RHE)与半波电位(0.835 V vs RHE)与商业化Pt/C相近,经过7 000 s后,Fe-N-C仍保持93.53%的相对电流,显示出优异的氧还原催化稳定性.
基金supported by the National Thousand Talents Plan of Chinathe National Natural Science Foundation of China(Grant Nos.21673014 and U1766216)+1 种基金the 111 project(B17002)funded by the Ministry of Education of Chinathe Fundamental Research Funds for the Central Universities of China
文摘Proton exchange membrane fuel cells(PEMFC)have attracted much attention because of their high energy conversion efficiency,high power density and zero emission of pollutants.However,the high cost of the cathode platinum group metal(PGM)catalysts creates a barrier for the large-scale application of PEMFC.Tremendous efforts have been devoted to the development of low-cost PGM-free catalysts,especially the Fe-N-C catalysts,to replace the expensive PGM catalysts.However,the characterization methods and evaluation standards of the catalysts varies,which is not conducive to the comparison of PGM-free catalysts.U.S.Department of energy(DOE)is the only authority that specifies the testing standards and activity targets for PGM-free catalysts.In this review,the major breakthroughs of Fe-N-C catalysts are outlined with the reference of DOE standards and targets.The preparation and characteristics of these highly active Fe-N-C catalysts are briefly introduced.Moreover,the efforts on improving the mass transfer and the durability issue of Fe-N-C fuel cell are discussed.Finally,the prospective directions concerning the comprehensive evaluation of the Fe-N-C catalysts are proposed.
基金supported by the National Natural Science Foundation of China(21633008,21433003,U1601211,21733004)National Science and Technology Major Project(2016YFB0101202)+1 种基金Jilin Province Science and Technology Development Program(20150101066JC,20160622037JC,20170203003SF,20170520150JH)Hundred Talents Program of Chinese Academy of Sciences and the Recruitment Program of Foreign Experts(WQ20122200077)
文摘Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the active site hosts, its hostility to electron/mass transfer could lead to the incomplete fulfillment of the catalytic activity. Besides, the formation of inactive metallic Fe particles during the conventional catalyst synthesis could also decrease the active site density and complicate the identification of real active site. Herein, we developed a facial hydrogen etching methodology to yield single site Fe-N-C catalysts featured with micro/mesoporous hierarchical structure. The hydrogen concentration in pyrolysis process was designated to effectively regulate the pore structure and active site density of the resulted catalysts.The optimized sample achieves excellent ORR catalytic performance with an ultralow H2O2 yield(1%)and superb stability over 10,000 cycles. Our finding provides new thoughts for the rational design of hierarchically porous carbon-based materials and highly promising non-precious metal ORR catalysts.
基金the financial support of the Fundamental Research Funds for the Central Universities (CCNU20QN007, CCNU20TS013)the Program of Introducing Talents of Discipline to Universities of China (111 program, B17019)the Recruitment Program of Global Youth Experts of China。
文摘Single-atom catalysts(SACs) with nitrogen-coordinated nonprecious metal sites have exhibited inimitable advantages in electrocatalysis.However,a large room for improving their activity and durability remains.Herein,we construct atomically dispersed Fe sites in N-doped carbon supports by secondary-atom-doped strategy.Upon the secondary doping,the density and coordination environment of active sites can be efficiently tuned,enabling the simultaneous improvement in the number and reactivity of the active site.Besides,structure optimizations in terms of the enlarged surface area and improved hydrophilicity can be achieved simultaneously.Due to the beneficial microstructure and abundant highly active FeN_5 moieties resulting from the secondary doping,the resultant catalyst exhibits an admirable half-wave potential of 0.81 V versus 0.83 V for Pt/C and much better stability than Pt/C in acidic media.This work would offer a general strategy for the design and preparation of highly active SACs for electrochemical energy devices.
