Self-Assembled Zn1-x O/TiO2 Nanocomposite as a Novel p-n Heterojunction for Selective CO2-to-CO Photoreduction

Selective CO2 photoreduction to valuable chemicalsispromising for a carbon-neutral future and still remains a challenge.Herein, Zn vacancy-rich ZnO (Zn1-x O) nanoparticles were used as cocatalyst to construct a Zn1-x O/TiO2 nanostructure via the self-assemblyprocess. The existence of Zn vacancies triggered the intimate contactbetween Zn1-x O and TiO2 through the Ti-O-Zn bonds. Theoretical and experimentalresults show that the hybridization of Zn1-x O and TiO2 resulted in the formation of a p-nheterojunction, leading to the enhanced separation efficiency of photoinducedelectron-hole pairs. As a result, the optimized Zn1-x O/TiO2 nanocomposite exhibited nearly100% selectivity of CO2-to-CO photoreduction, and the productivitywas 4.2 times higher than that of pristine TiO2. In situFourier transform infrared spectra along with theoretical calculationswere also conducted to investigate the mechanism of the selectivephotocatalytic CO2-to-CO process. It is concluded thatthe charge depletion on the TiO2 surface induced by thecharge transfer from Zn1-x O toTiO(2) can lower the energy barrier of CO* desorption andconvert the endothermic CO* desorption process into an exothermicreaction step, thus triggering selective CO production. This workprovides a new perspective on the rational fabrication of nanostructuresfor efficient and selective photocatalytic CO2 conversionthrough intermediate modulation.