Fe/N/C is a promising non-platinum catalyst for the oxygen reduction reaction （ORR）. Even so, mass transfer remains a challenge in the application of Fe/N/C to proton exchange membrane fuel cells, due to the high ca...Fe/N/C is a promising non-platinum catalyst for the oxygen reduction reaction （ORR）. Even so, mass transfer remains a challenge in the application of Fe/N/C to proton exchange membrane fuel cells, due to the high catalyst loadings required. In the present work, mesoporous Fe/N/C was syn- thesized through heat treatment of K]600 carbon black coated with poly-2-aminobenzimidazole and FeC13. The as-prepared Fe/N/C possesses a unique hollow-shell structure that contains a buffer zone allowing both water formation and vaporization, and also facilitates the mass transfer of gas- eous oxygen. This catalyst generated an oxygen reduction reaction activiW of 9.21 A/g in conjunc- tion with a peak power density of 0.71 W/cm2.展开更多
An environmentally friendly precursor, adenosine, has been used as a dual source of C and N to synthesize nitrogen-doped carbon catalyst with/without Fe. A hydrothermal carbonization method has been used and water is ...An environmentally friendly precursor, adenosine, has been used as a dual source of C and N to synthesize nitrogen-doped carbon catalyst with/without Fe. A hydrothermal carbonization method has been used and water is the carbonization media. The morphology of samples with/without Fe component has been compared by HRTEM, and the result shows that Fe can promote the graphitization of carbon. Further electro-chemical test shows that the oxygen reduction reaction（ORR） catalytic activity of Fe-containing sample（C–Fe N） is much higher than that of the Fe-free sample（C–N）. Additionally, the intermediates of C–Fe N formed during each synthetic procedure have been thoroughly characterized by multiple methods,and the function of each procedure has been discussed. The C–Fe N sample exhibits high electro-catalytic stability and superior electro-catalytic activity toward ORR in alkaline media, with its half-wave potential 20 mV lower than that of commercial Pt/C（40 wt%）. It is further incorporated into alkaline polymer electrolyte fuel cell（APEFC） as the cathode material and led to a power density of 100 m W/cm;.展开更多
The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the benchmark Pt/C catalyst in proton exchange membrane fuel cells(PEMFCs).However,the major bottleneck is its significant a...The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the benchmark Pt/C catalyst in proton exchange membrane fuel cells(PEMFCs).However,the major bottleneck is its significant activity decay in real-world PEMFC cells.The superposed“fast decay”and“slow decay”have been well documented to describe the degradation process of Fe/N/C catalysts during PEMFC operation.The fast decay has been well understood in close relation to the demetallation at the initial 15-h stability test.Nevertheless,it is still unclear how the remanent active sites evolve after demetallation.To this end,the catalyst performance and evolution of a typical Fe/N/C active site were herein investigated through postmortem characterizations of the membrane electrode assemblies(MEAs)after different operations.It is presented that 1 bar pressure and 80℃ temperature are the optimized conditions for Fe/N/C MEA.Particularly,the“fast decay”in the initial 15 h is immune to the various operating parameters,while the“slow decay”highly depends on the applied temperature and pressure.According to the X-ray absorption spectra(XAS)analysis and stability test of MEA,the gradual evolution of Fe-N coordination to Fe-O is found correlated with the“slow decay”and accounts for the catalyst decay after the demetallation process.展开更多
Fe/N/C material is the most competitive alternative to precious-metal catalysts for oxygen reduction.In view of the present consensus on active centers,further effort is directed at maximizing the density of single Fe...Fe/N/C material is the most competitive alternative to precious-metal catalysts for oxygen reduction.In view of the present consensus on active centers,further effort is directed at maximizing the density of single Fe atoms.Here,the imperfections in commonly used doping strategy of Fe for the synthesis of zeolitic imidazolateframework(ZIF)-derived Fe/N/C catalysts are revealed.More importantly,a strikingly improved catalyst is obtained by a‘second pyrolysis’method and delivers a half-wave potential of 0.825 V(vs.RHE)in acidic media.The strong confinement effect of carbonaceous host accounts for the formation of dense single-atom sites and thus the high activity.Our findings will potentially facilitate future improvement of M/N/C catalysts.展开更多
Pyrolyzed Fe/N/C catalyst has been considered as the most promising candidate to replace Pt for oxygen reduction reaction(ORR) in fuel cells.However,poor stability of Fe/N/C catalyst,mainly attributed to the oxidation...Pyrolyzed Fe/N/C catalyst has been considered as the most promising candidate to replace Pt for oxygen reduction reaction(ORR) in fuel cells.However,poor stability of Fe/N/C catalyst,mainly attributed to the oxidation corrosion by aggressive ·OH radical,severely hampers its applications.However,the exact mechanism for generation of ·OH is unclear yet.Herein,we developed a fluorescent method to effectively detect ·OH generated from ORR on Fe/N/C catalyst by using coumarin as a fluorescent probe.A great difference in potential dependence between ·OH and H2O2 generated from the ORR was observed,which suggests that ·OH is not generated from the decomposition of H2O2 as traditional viewpoint.展开更多
The low intrinsic activity of Fe/N/C oxygen catalysts restricts their commercial application in the fuel cells technique;herein,we demonstrated the interface engineering of plasmonic induced Fe/N/C-F catalyst with pri...The low intrinsic activity of Fe/N/C oxygen catalysts restricts their commercial application in the fuel cells technique;herein,we demonstrated the interface engineering of plasmonic induced Fe/N/C-F catalyst with primarily enhanced oxygen reduction performance for fuel cells applications.The strong interaction between F and Fe-N4 active sites modifies the catalyst interfacial properties as revealed by X-ray absorption structure spectrum and density functional theory calculations,which changes the electronic structure of Fe-N active site resulting from more atoms around the active site participating in the reaction as well as super-hydrophobicity from C–F covalent bond.The hybrid contribution from active sites and carbon support is proposed to optimize the three-phase microenvironment efficiently in the catalysis electrode,thereby facilitating efficient oxygen reduction performance.High catalytic performance for oxygen reduction and fuel cells practical application catalyzed by Fe/N/C-F catalyst is thus verified,which offers a novel catalyst system for fuel cells technique.展开更多
Fe/N/C catalysts,synthesized through the pyrolysis of Fe-doped metal–organic framework (MOF) precursors,have attracted extensive attention owing to their promising oxygen reduction reaction (ORR) catalytic activity i...Fe/N/C catalysts,synthesized through the pyrolysis of Fe-doped metal–organic framework (MOF) precursors,have attracted extensive attention owing to their promising oxygen reduction reaction (ORR) catalytic activity in fuel cells and/or metal-air batteries.However,post-treatments (acid washing,second pyrolysis,and so on) are unavoidable to improve ORR catalytic activity and stability.The method for introducing Fe^(3+) sources (anhydrous Fe Cl_(3)) into the MOF structure,in particular,is a critical step that can avoid time-consuming post-treatments and result in more exposed Fe-N_(x) active sites.Herein,three different Fe doping strategies were systematically investigated to explore their influence on the types of active sites formed and ORR performance.Fe-NC(Zn^(2+)),synthesized by one-step pyrolysis of Fe doped ZIF-8 (Zn^(2+)) precursor which was obtained by adding the anhydrous Fe Cl_(3)source into the Zn(NO_(3))_(2)·6H_(2)O/methanol solution before mixing,possessed the highest Fe-N_(x)active sites due to the high-efficiency substitution of Zn^(2+)ions with Fe^(3+) ions during ZIF-8 growth,the strong interaction between Fe^(3+) ions and N atoms of 2-Methylimidazole (2-MIm),and ZIF-8’s micropore confinement effect.As a result,Fe-NC(Zn^(2+)) presented high ORR activity in the entire p H range (p H=1,7,and 13).At p H=13,Fe-NC(Zn^(2+)) exhibited a half-wave potential (E1/2) of 0.95 V (vs.reversible hydrogen electrode),which was 70 m V higher than that of commercial Pt/C.More importantly,Fe-NC(Zn^(2+)) showed superior ORR stability in neutral media without performance loss after 5,000 cycles.A record-high open-circuit voltage(1.9 V) was obtained when Fe-NC(Zn^(2+)) was used as a cathodic catalyst in assembled Mg-air batteries in neutral media.The assembled liquid and all-solid Mg-air batteries with high performance indicated that Fe-NC(Zn^(2+)) has enormous potential for use in flexible and wearable Mg-air batteries.展开更多
文摘研制高活性的Fe/N/C氧还原催化剂对于降低燃料电池成本、实现商业化应用有重要意义.为实现Fe/N/C催化剂的理性设计,需要深入研究其活性位结构.本文发展一种研究活性位结构的新策略,以预先合成好的聚间苯二胺基Fe/N/C催化剂(Pm PDA-Fe Nx/C)为起始物,对其在1000~1500 o C高温下再次进行热处理并使其失活,通过关联催化剂热处理前后的结构变化与氧还原催化性能来揭示活性位结构.实验结果表明,随着热处理温度升高,活性中心结构被破坏,铁原子析出团聚并形成纳米颗粒,氮元素挥发损失,导致催化剂失活.XPS分析显示,低结合能含氮物种的含量与催化剂的ORR活性呈良好的正相关性,表明活性中心很可能是由吡啶N和Fe-N物种构成的.
基金supported by the National Basic Research Program of Chain(973 Program,2015CB932300)the National Natural Science Foundation of China(21373175,21321062,21361140374)Fundamental Research Funds for the Central Universities(20720150109)
文摘Fe/N/C is a promising non-platinum catalyst for the oxygen reduction reaction （ORR）. Even so, mass transfer remains a challenge in the application of Fe/N/C to proton exchange membrane fuel cells, due to the high catalyst loadings required. In the present work, mesoporous Fe/N/C was syn- thesized through heat treatment of K]600 carbon black coated with poly-2-aminobenzimidazole and FeC13. The as-prepared Fe/N/C possesses a unique hollow-shell structure that contains a buffer zone allowing both water formation and vaporization, and also facilitates the mass transfer of gas- eous oxygen. This catalyst generated an oxygen reduction reaction activiW of 9.21 A/g in conjunc- tion with a peak power density of 0.71 W/cm2.
基金financially supported by the National Natural Science Foundation of China(21573167,21633008,91545205,21125312)National Key Research and Development Program(2016YFB0101203)+2 种基金the National Basic Research Program(2012CB932800,2012CB215500)the Doctoral Fund of Ministry of Education of China(20110141130002)the Fundamental Research Funds for the Central Universities(2014203020207)
文摘An environmentally friendly precursor, adenosine, has been used as a dual source of C and N to synthesize nitrogen-doped carbon catalyst with/without Fe. A hydrothermal carbonization method has been used and water is the carbonization media. The morphology of samples with/without Fe component has been compared by HRTEM, and the result shows that Fe can promote the graphitization of carbon. Further electro-chemical test shows that the oxygen reduction reaction（ORR） catalytic activity of Fe-containing sample（C–Fe N） is much higher than that of the Fe-free sample（C–N）. Additionally, the intermediates of C–Fe N formed during each synthetic procedure have been thoroughly characterized by multiple methods,and the function of each procedure has been discussed. The C–Fe N sample exhibits high electro-catalytic stability and superior electro-catalytic activity toward ORR in alkaline media, with its half-wave potential 20 mV lower than that of commercial Pt/C（40 wt%）. It is further incorporated into alkaline polymer electrolyte fuel cell（APEFC） as the cathode material and led to a power density of 100 m W/cm;.
基金financially supported by the Fundamental Re-search Funds for the Central Universities(No.2023CDJXY-016)the Outstanding Youth Project of Natural Science Foundation of Guangdong Province(Grant No.2022B1515020020).
文摘The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the benchmark Pt/C catalyst in proton exchange membrane fuel cells(PEMFCs).However,the major bottleneck is its significant activity decay in real-world PEMFC cells.The superposed“fast decay”and“slow decay”have been well documented to describe the degradation process of Fe/N/C catalysts during PEMFC operation.The fast decay has been well understood in close relation to the demetallation at the initial 15-h stability test.Nevertheless,it is still unclear how the remanent active sites evolve after demetallation.To this end,the catalyst performance and evolution of a typical Fe/N/C active site were herein investigated through postmortem characterizations of the membrane electrode assemblies(MEAs)after different operations.It is presented that 1 bar pressure and 80℃ temperature are the optimized conditions for Fe/N/C MEA.Particularly,the“fast decay”in the initial 15 h is immune to the various operating parameters,while the“slow decay”highly depends on the applied temperature and pressure.According to the X-ray absorption spectra(XAS)analysis and stability test of MEA,the gradual evolution of Fe-N coordination to Fe-O is found correlated with the“slow decay”and accounts for the catalyst decay after the demetallation process.
基金The work was supported by the National Natural Science Foundation of China(Nos.21633008,21875243,and 21603216)the National Science and Technology Major Project(No.2017YFB01029002)Jilin Province Science and Technology Development Program(Nos.20190201270JC and 20180101030JC).
文摘Fe/N/C material is the most competitive alternative to precious-metal catalysts for oxygen reduction.In view of the present consensus on active centers,further effort is directed at maximizing the density of single Fe atoms.Here,the imperfections in commonly used doping strategy of Fe for the synthesis of zeolitic imidazolateframework(ZIF)-derived Fe/N/C catalysts are revealed.More importantly,a strikingly improved catalyst is obtained by a‘second pyrolysis’method and delivers a half-wave potential of 0.825 V(vs.RHE)in acidic media.The strong confinement effect of carbonaceous host accounts for the formation of dense single-atom sites and thus the high activity.Our findings will potentially facilitate future improvement of M/N/C catalysts.
基金supported by the National Key Research and Development Program of China(2017YFA0206500)the National Natural Science Foundation of China(21603103,21875194,21902125,91645121)
文摘Pyrolyzed Fe/N/C catalyst has been considered as the most promising candidate to replace Pt for oxygen reduction reaction(ORR) in fuel cells.However,poor stability of Fe/N/C catalyst,mainly attributed to the oxidation corrosion by aggressive ·OH radical,severely hampers its applications.However,the exact mechanism for generation of ·OH is unclear yet.Herein,we developed a fluorescent method to effectively detect ·OH generated from ORR on Fe/N/C catalyst by using coumarin as a fluorescent probe.A great difference in potential dependence between ·OH and H2O2 generated from the ORR was observed,which suggests that ·OH is not generated from the decomposition of H2O2 as traditional viewpoint.
基金the National Natural Science Foundation of China(Nos.21203008 and 21975025)Beijing Nature Science Foundation(No.2172051)+1 种基金State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,Donghua University,and Shenzhen Science and Technology Innovation Committee(No.JCYJ20170817161445322)Thanks for Dr.Lirong Zheng(1W1B@Beijing Synchrotron Radiation Facility)for providing measurement time.We appreciate help from Dr.Jiaou Wang(4B9B@Beijing Synchrotron Radiation Facility)for XANES measurement.XPS measurements were performed in the Analysis&Testing Center,Beijing Institute of Technology.
文摘The low intrinsic activity of Fe/N/C oxygen catalysts restricts their commercial application in the fuel cells technique;herein,we demonstrated the interface engineering of plasmonic induced Fe/N/C-F catalyst with primarily enhanced oxygen reduction performance for fuel cells applications.The strong interaction between F and Fe-N4 active sites modifies the catalyst interfacial properties as revealed by X-ray absorption structure spectrum and density functional theory calculations,which changes the electronic structure of Fe-N active site resulting from more atoms around the active site participating in the reaction as well as super-hydrophobicity from C–F covalent bond.The hybrid contribution from active sites and carbon support is proposed to optimize the three-phase microenvironment efficiently in the catalysis electrode,thereby facilitating efficient oxygen reduction performance.High catalytic performance for oxygen reduction and fuel cells practical application catalyzed by Fe/N/C-F catalyst is thus verified,which offers a novel catalyst system for fuel cells technique.
基金supported by the National Natural Science Foundation of China(22171266)the FJIRSM&IUE Joint Research Fund(RHZX-2019-002)+2 种基金the STS Project(KFJ-STS-QYZD-2021-09002)the National Key Basic Research Program of China(2017YFA0403402)the Project of the National Natural Science Foundation of China(U1932119)。
文摘Fe/N/C catalysts,synthesized through the pyrolysis of Fe-doped metal–organic framework (MOF) precursors,have attracted extensive attention owing to their promising oxygen reduction reaction (ORR) catalytic activity in fuel cells and/or metal-air batteries.However,post-treatments (acid washing,second pyrolysis,and so on) are unavoidable to improve ORR catalytic activity and stability.The method for introducing Fe^(3+) sources (anhydrous Fe Cl_(3)) into the MOF structure,in particular,is a critical step that can avoid time-consuming post-treatments and result in more exposed Fe-N_(x) active sites.Herein,three different Fe doping strategies were systematically investigated to explore their influence on the types of active sites formed and ORR performance.Fe-NC(Zn^(2+)),synthesized by one-step pyrolysis of Fe doped ZIF-8 (Zn^(2+)) precursor which was obtained by adding the anhydrous Fe Cl_(3)source into the Zn(NO_(3))_(2)·6H_(2)O/methanol solution before mixing,possessed the highest Fe-N_(x)active sites due to the high-efficiency substitution of Zn^(2+)ions with Fe^(3+) ions during ZIF-8 growth,the strong interaction between Fe^(3+) ions and N atoms of 2-Methylimidazole (2-MIm),and ZIF-8’s micropore confinement effect.As a result,Fe-NC(Zn^(2+)) presented high ORR activity in the entire p H range (p H=1,7,and 13).At p H=13,Fe-NC(Zn^(2+)) exhibited a half-wave potential (E1/2) of 0.95 V (vs.reversible hydrogen electrode),which was 70 m V higher than that of commercial Pt/C.More importantly,Fe-NC(Zn^(2+)) showed superior ORR stability in neutral media without performance loss after 5,000 cycles.A record-high open-circuit voltage(1.9 V) was obtained when Fe-NC(Zn^(2+)) was used as a cathodic catalyst in assembled Mg-air batteries in neutral media.The assembled liquid and all-solid Mg-air batteries with high performance indicated that Fe-NC(Zn^(2+)) has enormous potential for use in flexible and wearable Mg-air batteries.
