Fe-N-C core-shell catalysts with single low-spin Fe(Ⅱ)-N_(4)species for oxygen reduction reaction and high-performance proton exchange membrane fuel cells  

作　　者：Yan Wan Linhui Yu Bingxin Yang Caihong Li Chen Fang Wei Guo Fang-Xing Xiao Yangming Lin 

机构地区：[1]Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials,Xiamen Institute of Rare Earth Materials,Haixi Institute,Chinese Academy of Sciences,Xiamen 361021,Fujian,China [2]CAS Key Laboratory of Urban Pollutant Conversion,Institute of Urban Environment,Chinese Academy of Sciences,Xiamen 361021,Fujian,China [3]Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences,Fuzhou 350002,Fujian,China [4]College of Materials Science and Engineering,Fuzhou University,New Campus,Minhou 350108,Fujian,China [5]College of Chemistry and Materials Science,Fujian Normal University,Fuzhou 350117,Fujian,China

出　　处：《Journal of Energy Chemistry》2024年第6期538-546,I0013,共10页能源化学（英文版）

基　　金：financial support from the“Hundred Talents Program”of the Chinese Academy of Sciences;the“Young Talents Training Program”of the Shanghai Branch of the Chinese Academy of Sciences;the financial support from the Xiamen City Natural Science Foundation of China(3502Z20227085,3502Z20227256);the National Science Youth Foundation of China(22202205);the Fujian Provincial Natural Science Foundation of China(2022J01502);Open Source Foundation of State Key Laboratory of Structural Chemistry。

摘　　要：Fe-N-doped carbon materials(Fe-N-C)are promising candidates for oxygen reduction reaction(ORR)relative to Pt-based catalysts in proton exchange membrane fuel cells(PEMFCs).However,the intrinsic contributions of Fe-N_(4)moiety with different chemical/spin states(e.g.D1,D2,D3)to ORR are unclear since various states coexist inevitably.In the present work,Fe-N-C core-shell nanocatalyst with single lowspin Fe(Ⅱ)-N_(4)species(D1)is synthesized and identified with ex-situ ultralow temperature Mossbauer spectroscopy(T=1.6 K)that could essentially differentiate various Fe-N_(4)states and invisible Fe-O species.By quantifying with CO-pulse chemisorption,site density and turnover frequency of Fe-N-C catalysts reach 2.4×10^(-9)site g^(-1)and 23 e site~(-1)s^(-1)during the ORR,respectively.Half-wave potential(0.915V_(RHE))of the Fe-N-C catalyst is more positive(approximately 54 mV)than that of Pt/C.Moreover,we observe that the performance of PEMFCs on Fe-N-C almost achieves the 2025 target of the US Department of Energy by demonstrating a current density of 1.037 A cm^(-2)combined with the peak power density of 0,685 W cm^(-2),suggesting the critical role of Fe(Ⅱ)-N_(4)site(D1).After 500 h of running,PEMFCs still deliver a power density of 1.26 W cm^(-2)at 1.0 bar H_(2)-O_(2),An unexpected rate-determining step is figured out by isotopic labelling experiment and theoretical calculation.This work not only offers valuable insights regarding the intrinsic contribution of Fe-N_(4)with a single spin state to alkaline/acidic ORR,but also provides great opportunities for developing high-performance stable PEMFCs.

关 键 词：Fuel cells Oxygen reduction reaction Non-platinum group metals(PGMs) Isotopic labelling Active site TOF 

分 类 号：TQ426[化学工程] TM911.4[电气工程—电力电子与电力传动]