Construction of an all-solid-state artificial Z-scheme system consisting of Bi₂WO₆/Au/CdS nanostructure for photocatalytic CO₂ reduction into renewable hydrocarbon fuel

An all-solid-state Bi₂WO₆/Au/CdS Z-scheme system was constructed for the photocatalytic reduction of CO₂ into methane in the presence of water vapor. This Z-scheme consists of ultrathin Bi₂WO₆ nanoplates and CdS nanoparticles as photocatalysts, and a Au nanoparticle as a solid electron mediator offering a high speed charge transfer channel and leading to more efficient spatial separation of electron-hole pairs. The photo-generated electrons from the conduction band (CB) of Bi₂WO₆ transfer to the Au, and then release to the valence band (VB) of CdS to recombine with the holes of CdS. It allows the electrons remaining in the CB of CdS and holes in the VB of Bi₂WO₆ to possess strong reduction and oxidation powers, respectively, leading the Bi₂WO₆/Au/CdS to exhibit high photocatalytic reduction of CO₂, relative to bare Bi₂WO₆, Bi₂WO₆/Au, and Bi₂WO₆/CdS. The depressed hole density on CdS also enhances the stability of the CdS against photocorrosion.