Rational design of an air-breathing gas-diffusion electrode with oxygen vacancy-rich ZnO for robust and durable H₂O₂ electrosynthesis

Abstract

Developing cost-effective and durable cathodes with outstanding oxygen mass transport and selective two-electron oxygen reduction reaction (ORR) is crucial for large-scale H2O2 electrosynthesis. Herein, an oxygen vacancy-rich ZnO-modified air-breathing gas-diffusion electrode (ZnO-V/GDE) was fabricated, thus eliminating the cost of aeration while achieving remarkable O2 utilization efficiency and H2O2 selectivity. This novel cathode led to ultrahigh H2O2 yield of 1005.2 mg L−1 with selectivity of 74.6 %, outperforming both the raw and ZnO-modified air-breathing GDEs. Moreover, the practical applicability of ZnO-V/GDE was demonstrated by its high stability and effectiveness when treating micropollutants in wastewater by ZnO-V/GDE-based electro-Fenton process. Mechanistic insights unveiled the key roles of oxygen vacancies, which not only facilitate the O2 transport by creating a superhydrophobic interface and provide binding centers to O2, but also reduce the energy barrier of the rate-determining step (OOH*-to-H2O2), eventually enhancing the ORR performance.