Acidic and Alkaline pH Controlled Oxygen Reduction Reaction Pathway over Co‐N 4 C Catalyst

作者：Bikash Mahapatra, Pranjit Barman, D. Panigrahi, Sachin Kochrekar, Bappi Paul, Abhishek Panghal, Anil Kumar U., Vishal M. Dhavale, Mukul Gupta, Deepak Kumar, Vijay Kumar, Santosh K. Singh · 发表于：Small · 年份：2024 · DOI：10.1002/smll.202405530 · 被引用次数：9 · 研究领域：Electrocatalysts for Energy Conversion、Fuel Cells and Related Materials、Advanced Memory and Neural Computing

Abstract Enhanced oxygen reduction reaction (ORR) kinetics and selectivity are crucial to advance energy technologies like fuel cells and metal–air batteries. Single‐atom catalysts (SACs) with M‐N 4 /C structure have been recognized to be highly effective for ORR. However, the lack of a comprehensive understanding of the mechanistic differences in the activity under acidic and alkaline environments is limiting the full potential of the energy devices. Here, a porous SAC is synthesized where a cobalt atom is coordinated with doped nitrogen in a graphene framework (pCo‐N 4 C). The resulting pCo‐N 4 C catalyst demonstrates a direct 4e − ORR process and exhibits kinetics comparable to the state‐of‐the‐art (Pt/C) catalyst. Its higher activity in an acidic electrolyte is attributed to the tuned porosity‐induced hydrophobicity. However, the pCo‐N 4 C catalyst displays a difference in ORR activity in 0.1 m HClO 4 and 0.1 m KOH, with onset potentials of 0.82 V and 0.91 V versus RHE, respectively. This notable activity difference in acidic and alkaline media is due to the protonation of coordinated nitrogen, restricted proton coupled electron transfer (PCET) at the electrode/electrolyte interface. The effect of pH over the catalytic activity is further verified by Ab‐initio molecular dynamics (AIMD) simulations using density functional theory (DFT) calculations.