Defective-Engineered ZnO Encapsulated in N-Doped Carbon for Sustainable 2e^– ORR: Interfacial Zn–N Bond Regulated Oxygen Reduction Pathways

Abstract

Zinc oxide (ZnO), although known for its stability and safety, has shown limited catalytic activity in the two-electron oxygen reduction reaction (2e– ORR). In this context, we synthesized a robust defective-engineered ZnO/N-doped graphene heterojunction (ZnO-NG) featuring abundant Zn–N bonds at the interface. The engineered composite exhibited a remarkable H2O2 yield of 13.1 mg h–1 cm–2 at 25 mA cm–2 with H2O2 selectivity of 85.0%, surpassing NG and ZnO counterparts. Furthermore, the exceptional long-term stability of ZnO-NG was validated through chronoamperometric measurements and 10 successive runs, highlighting its great potential for large-scale H2O2 synthesis. Density functional theory calculations and X-ray absorption near-edge structure analysis revealed that interfacial bridging N regulated the local electron distribution, transferring the unpaired electrons from Zn sites to the adjacent N/C atoms. The configuration facilitated the hydrogenation step of O2-to-OOH* and more importantly inhibited the O*-to–OH* conversion, thereby improving the selectivity in 2e– ORR toward water remediation.