Branch-like Cd_xZn_1-xSe/Cu₂O@Cu step-scheme heterojunction for CO₂ photoreduction

The solar driven reduction of carbon dioxide (CO₂) to high value-added carbon based fuel is a promising solution to mitidate climate and energy problems, however, improving the adsorption and conversion efficiency of CO₂ in the photoreduction process still faces severe challenges. In this work, Cd_0·7Zn_0·3Se solid solution was prepared by cation exchange: selenium (Se) vacancies are produced during ion exchange, which promotes the unsaturated coordination of the surrounding metal atoms. The adsorption of diethylenetriamine (DETA) on the surface limits the growth of Cd_xZn_1-xSe crystallites, resulting in insufficient coordination of the surface atoms, which then become active adsorption sites. Furthermore, a heterojunction was formed with Cu₂O@Cu to accelerate the separation and transfer of photo-induced carriers of Cd_0·7Zn_0·3Se, and the optimized Cd_0·7Zn_0·3Se/Cu₂O@Cu (CZS/CC) step-scheme heterojunction exhibited a CO release activity of 50.5 μmol g⁻¹ h⁻¹, which is 3.8 and 10.7 times higher than that of Cd_0·7Zn_0·3Se and Cu₂O@Cu, respectively. This work is expected to open up new insight for the regulation of nanostructures and the design of selective catalysts.