Oxidation Evolution and Activity Origin of N-Doped Carbon in the Oxygen Reduction Reaction

作者：Jiaqi Wu, Chuanqi Cheng, Shanshan Lu, Bin Zhang, Yanmei Shi · 发表于：Transactions of Tianjin University · 年份：2024 · DOI：10.1007/s12209-024-00406-0 · 被引用次数：13 · 研究领域：Electrocatalysts for Energy Conversion、Catalytic Processes in Materials Science、Advanced battery technologies research

Abstract N-doped carbon materials, with their applications as electrocatalysts for the oxygen reduction reaction (ORR), have been extensively studied. However, a negletcted fact is that the operating potential of the ORR is higher than the theoretical oxidation potential of carbon, possibly leading to the oxidation of carbon materials. Consequently, the influence of the structural oxidation evolution on ORR performance and the real active sites are not clear. In this study, we discover a two-step oxidation process of N-doped carbon during the ORR. The first oxidation process is caused by the applied potential and bubbling oxygen during the ORR, leading to the oxidative dissolution of N and the formation of abundant oxygen-containing functional groups. This oxidation process also converts the reaction path from the four-electron (4e) ORR to the two-electron (2e) ORR. Subsequently, the enhanced 2e ORR generates oxidative H 2 O 2 , which initiates the second stage of oxidation to some newly formed oxygen-containing functional groups, such as quinones to dicarboxyls, further diversifying the oxygen-containing functional groups and making carboxyl groups as the dominant species. We also reveal the synergistic effect of multiple oxygen-containing functional groups by providing additional opportunities to access active sites with optimized adsorption of OOH*, thus leading to high efficiency and durability in electrocatalytic H 2 O 2 production.