Electrochemical probing into the active sites of graphitic-layer encapsulated iron oxygen reduction reaction electrocatalysts

作     者：Lijie Zhong Jens Oluf Jensen Lars Nilausen Cleemann Chao Pan Qingfeng Li 

作者机构：Department of Energy Conversion and Storage Technical University of Denmark 

出 版 物：《Science Bulletin》 (科学通报（英文版）)

年 卷 期：2018年第63卷第1期

页      面：24-30页

核心收录：

学科分类：0808[工学-电气工程] 081705[工学-工业催化] 08[工学] 0817[工学-化学工程与技术] 

基　　金：supported by Innovation Fond Denmark(4M Centre 0603-00527B and Non-Precious 4106-00012B) Forsk EL Program(UPCAT 2015-1-12315) 

主　　题：Encapsulated Fe catalysts Oxygen reduction reaction Ion poisoning Active sites NPMCs 

摘      要：The graphitic-layer encapsulated iron-containing nanoparticles(G@Fe) have been proposed as a potential type of active and stable non-precious metal electrocatalysts(NPMCs) for the oxygen reduction reaction(ORR). However, the contribution of the encapsulated components to the ORR activity is still unclear compared with the well-recognized surface coordinated FeN_x/C structure. Using the strong complexing effect of the iron component with anions, cyanide(CN^-) in alkaline and thiocyanate(SCN^-) in acidic media, the metal containing active sites are electrochemically probed. Three representative catalysts are chosen for a comparison including the as-prepared encapsulated G@Fe, commercial Fe/N/C catalyst with iron–nitrogen coordinated surface functionalities and molecular iron phthalocyanine(Fe Pc) containing well-defined structures and compositions. It was found that all samples showed significant shifts of half-wave potentials indicating that surface Fe coordinated sites in all cases. The G@Fe catalyst showed the weakest poisoning effect(the lowest shifts of half-wave potential) compared to the Fe/N/C and Fe Pc catalysts in both electrolytes. These results could be explained that the encapsulated iron components influence the FeN_x/C and/or N_xC surface functionality.