溶解
电催化剂
密度泛函理论
催化作用
化学
石墨烯
铂金
质子交换膜燃料电池
金属
无机化学
化学工程
计算化学
电化学
材料科学
电极
纳米技术
物理化学
有机化学
工程类
作者
Edward F. Holby,Guofeng Wang,Piotr Zelenay
出处
期刊:ACS Catalysis
日期:2020-11-24
卷期号:10 (24): 14527-14539
被引量:98
标识
DOI:10.1021/acscatal.0c02856
摘要
Platinum group metal-free (PGM-free) materials based on pyrolyzed M–N–C precursors offer a promising approach to replacing rare and expensive platinum group metal-based oxygen reduction reaction (ORR) electrocatalysts in proton exchange fuel cells (PEFCs). A major issue, however, is the stability of these materials in acidic environments and at potentials experienced in situ in PEFC cathodes and rotating disk electrode (RDE) experiments. Density functional theory (DFT)-based approaches have been valuable to understand how atomic scale structures couple to ORR activity. Little has been reported, however, on quantification of active site structure stability. This work proposes a set of DFT-accessible descriptors for M dissolution (demetalation) that directly address this need. Through the application of this approach to a specific Fe–N4 bilayer graphene-hosted active site structure, the roles of the environment (pH and potential), ORR intermediates, and graphene underlayers are explored. Ranges of stability are reported and hypotheses explaining previously reported experimental behavior based on these findings are proposed. In particular, proposed are model implications for experimental trends in stability with respect to alkaline and acidic conditions; experimental trends for dissolution to occur below a given potential; and observed discrepancies in stability for materials in O2-bearing vs O2-purged environments. Based on these findings, suggestions for improving active site resistance to metal dissolution are provided.
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