Elucidation and modulation of active sites in holey graphene electrocatalysts for <scp>H<sub>2</sub>O<sub>2</sub></scp> production
Ki Hwan Koh, Amir Hassan Bagherzadeh Mostaghimi, Qiaowan Chang, Yu Joong Kim, Samira Siahrostami, Tae Hee Han, Zheng Chen
Abstract
Abstract Selective electrochemical oxygen reduction (ORR) toward a two‐electron (2e − ) pathway is an eco‐friendly alternative method for H 2 O 2 synthesis to replace the energy‐intensive anthraquinone oxidation process. Carbon‐based electrocatalysts (CBEs) show great potential for practical H 2 O 2 synthesis. However, their complex structures make it challenging to determine the nature of active sites and to precisely control them. Herein, we show that precise modulation of the chemistry and structures of holey graphene with edge sites enriched by oxygen‐containing functional groups can facilitate 2e − ORR. These combined functionalities could improve ORR performance under various pH conditions, for example, resulting in an average of 95% H 2 O 2 selectivity, ~97% Faraday efficiency, high productivity of 2360 mol kg cat −1 h −1 in alkaline media. Density functional theory calculations on the oxygen functional groups at the edge sites revealed the most active site for 2e − ORR is a synergy between ether (COC) and carbonyl (CO) functional groups with nearly zero overpotential. image