Recyclable Composites of Mo/Fe Co-Doped ZnO1−x/Cu2O for Enhanced Photocatalytic Nitrogen Fixation

Abstract

A layer of Cu2O crystal film and ZnO nanoparticles doped with bimetallic Mo and Fe were successively grown on the surface of a copper mesh, which was applied in a liquid membrane photoreaction apparatus for photocatalytic nitrogen reduction reaction (PNRR). The characterization results indicate that the excellent ammonia yield benefits mainly from the synergistic effect of bimetallic doping, moderate oxygen vacancies (OVs), and p-n heterojunction. Surface defects caused by in situ doping of Mo and Fe ions act as active centers to capture and migrate electrons from the catalyst to adsorbed N2 molecule. With the introduction of bimetallic ions, the formation of more mesoporous enlarges the specific surface area, causing abundant reaction sites on the surface of the catalyst, which enhances the adsorption and activation of dinitrogen molecules. The existence of oxygen vacancy reduces the band gap and enhances the absorption of visible light. Furthermore, the p-n heterostructure promotes the effective transfer and separation of photogenerated carriers. Compared with the original Cu2O or ZnO, the photocatalytic ammonia yield of Mo–Fe co-doped ZnO/Cu2O is increased by 6.6 and 7.3 times, respectively, reaching 119.42 μmol cm−2 h−1.