Bimetallic dopants regulated electronic structures of ZnO nanorods for boosting solar-driven CO2 reduction

Although ZnO has potential application in photocatalytic CO2 reduction, it faces challenges such as limited light absorption range and high recombination of photo-induced electron/hole pairs. Given this, it is necessary to continuously explore new design strategies and optimization approaches to improve the performance of ZnO in photocatalytic CO2 reduction. In this work, ZnO nanorods (NRs) doped with Cu, Fe, and co-doped Cu/Fe are successfully synthesized through chemical displacement reaction obtaining precursors of uniformly dispersed dopants and subsequent treatments of radio-frequency (RF) thermal plasma technology. The effects of doping species and amounts on the oxygen vacancies and photocatalytic performances of ZnO are systematically investigated. The results indicate that (i) the introduction of metal cation dopants can effectively reduce the intrinsic band gap structure of ZnO, leading to broaden light absorption range in the visible light region and improving light utilization efficiency and (ii) the defects introduced by doping suppress the recombination of photo-generated charge carriers. The synergistic effect of the two aspects improves the photocatalytic activity in CO2 reduction. Especially, the bimetallic co-doped sample possesses much more oxygen vacancies with a bandgap of 2.71 eV, exhibiting optimal photocatalytic performance and cycling stability. This study has brought breakthroughs and progress in the field of photocatalytic CO2 reduction, including but not limited to, expanding the synthesis and regulation strategies of metal oxide semiconductor photocatalysts.