Significant Enhancement of Photocatalytic Reduction of CO2 with H2O over ZnO by the Formation of Basic Zinc Carbonate

Electron-hole pair separation efficiency and adsorption performance of photocatalysts to CO2 are the two key factors affecting the performance of photocatalytic CO2 reduction with H2O. Distinct from conventional promoter addition, this study proposed a novel approach to address these two issues by tuning the own surface features of semiconductor photocatalyst. Three ZnO samples with different morphologies, surface area, and defect content were fabricated by varying preparation methods, characterized by XRD, TEM, and room-temperature PL spectra, and tested in photoreduction of CO2 with H2O. The results show that the as-prepared porous ZnO nanosheets exhibit a much higher activity for photoreduction of CO2 with H2O when compared to ZnO nanoparticles and nanorods attributed to the existence of more defect sites, that is, zinc and oxygen vacancies. These defects would lower the combination rate of electron-hole pair as well as promote the formation of basic zinc carbonate by Lewis acid-base interaction, which is the active intermediate species for photoreduction of CO2. ZnO nanoparticles and ZnO nanorods with few defects show weak adsorption for CO2 leading to the inferior photocatalytic activities. This work provides new insight on the CO2 activation under light irradiation.