Greatly boosted H2O2 activity in two-electron water oxidation reaction on Zn-based catalysts by doping engineering

Abstract

Electrocatalytic production of hydrogen peroxide (H2O2) by two electron water oxidation reaction (2e-WOR) is an environmental process with low cost and devoid of H2O2 storage and transportation. ZnO is one of the important promising 2e-WOR catalysts with relatively high activity and selectivity of H2O2. However, the active sites and the effects of oxygen defects of ZnO remain unknown, which hampers the further improvement in H2O2 formation. To explore the active sites and develop Zn-based catalysts with high performance, Ni, Cu and Co ions are chosen to form M0.1Zn0.9O (M = Ni, Cu and Co) catalysts. Combining the experimental results with density functional theory (DFT) calculations, the active site of 2e-WOR on Zn-based catalysts is first discovered to be the 3-coordinated surface Zn without surface oxygen defects since oxygen defects result in a strong interaction of ·OH with catalyst and then impede the 2e-WOR process. Catalysts with high activity and selectivity for 2e-WOR should have small nano-particle sizes without oxygen defects. Co0.1Zn0.9O is obtained with high activity (35.3 mmol min−1·gcat−1) and selectivity (82%) of H2O2 at 3.2 V vs RHE. This work provides valuable perspectives for designing and developing high-performing catalysts in 2e-WOR reaction.