ZnSe/CdSe Z-scheme composites with Se vacancy for efficient photocatalytic CO2 reduction

ZnSe/CdSe are constructed by epitaxial growth of CdSe on ZnSe via cation-exchange reaction, which exhibit remarkable CO2 photoreduction performance due to formation of Z-scheme at the interface, high CO2 adsorption caused by Se vacancy, and improved light harvesting. [Display omitted] •ZnSe/CdSe is prepared by epitaxial growth of CdSe on ZnSe via ion exchange reaction.•High performance of CO2 photoreduction is achieved upon the CdSe loading on ZnSe.•Se vacancy that can enhance CO2 adsorption is created upon heterojunction formation.•Efficient charge transfer at ZnSe/CdSe interface follows the Z-scheme pathway.•Light harvesting is enhanced when ZnSe is modified by CdSe nanoparticles. A fundamental challenge in CO2 photoreduction is to establish highly efficient photocatalysts with efficient charge separation, wide-spectrum absorption and effective CO2 adsorption. The former two can be achieved by fabricating Z-scheme systems with narrow-bandgap semiconductor, and the last can be realized by creating vacancy defects in the catalyst. Herein, ZnSe/CdSe composites with different ZnSe/CdSe ratios are prepared via epitaxial growth of CdSe on ZnSe nanoparticles, which exhibit much higher CO2 photoreduction performance than pristine ZnSe under visible-light irradiation. ZnSe/CdSe (precursor ratio Zn:Cd = 1:0.125) exhibits an optimal CO yield (116.9 μmol g−1), which is 33.4 times that of pristine ZnSe (3.5 μmol g−1). Electron spin resonance (ESR) and density functional theory (DFT) calculations reveal that charge transfer at the ZnSe/CdSe interface follows Z-scheme pathway. Improved light harvesting by loading CdSe can further promote charge generation. Se vacancy generated during the preparation can facilitate CO2 adsorption.