Construction of a ZnIn₂S₄/Au/CdS Tandem Heterojunction for Highly Efficient CO₂Photoreduction

Photocatalytic CO₂ reduction technology is of great importance to alleviate energy crisis and environmental pollution; however, it remains a serious challenge due to the fast recombination of carriers. In this study, we report a three-dimensional structure of a ZnIn₂ S₄ /Au/CdS composite photocatalyst for the CO₂ reduction reaction, where Au nanoparticles (NPs) are evenly anchored on the surface of ZnIn₂ S₄ by photodeposition and Au NPs are wrapped around by CdS. In ZnIn₂ S₄ /Au/CdS composite photocatalysts, Au NPs act as a bridge to construct a "semiconductor-metal-semiconductor" tandem electron transfer mechanism (ZnIn₂ S₄ → Au → CdS) heterojunction, which greatly promotes the transfer of photogenerated electrons. It is worth noting that Au NPs, as a local surface plasmon resonance (LSPR) effect excited source to generate excited-state electrons, further improve the photoreduction CO₂ activity. Under UV-vis light irradiation, the CO yield of ZnIn₂ S₄ /Au/CdS can reach 63.07 μmol·g^-1·h^-1, which is higher than that of 6.37 μmol·g^-1·h^-1for pure ZnIn₂ S₄, 0.93 μmol·g^-1·h^-1for CdS, 8.9 μmol·g^-1·h^-1for ZnIn₂ S₄ /CdS, 31.04 μmol·g^-1·h^-1for ZnIn₂ S₄ /Au, and 5.37 μmol·g^-1·h^-1for CdS/Au. In addition, the ternary ZnIn₂ S₄ /Au/CdS composite photocatalyst has good cyclic stability. This study broadens the idea of designing photocatalysts with good carrier separation efficiency.