Metal phosphide modified CdxZn1-xS solid solutions as a highly active visible-light photocatalyst for hydrogen evolution

To promote and stabilize the photocatalytic activity of host photocatalyst, cost-effective and earth-abundant phosphides used as co-catalysts for replacing noble metals have attracted increasing attention in recent years. In this study, numerous transition metal phosphides, such as Cu3P, CoP, Ni2P and Fe2P nanoparticles, were prepared and then combined with CdxZn1-xS solid solution. The binary CdxZn1-xS/phosphide nanocomposites show higher photocatalytic activity of hydrogen generation than that of pure CdxZn1-xS solid solution. Remarkably, the photocatalytic rate of hydrogen production over the optimized Cd0.5Zn0.5S (CZS5)/Cu3P-0.3% (0.3 wt%) sample reached up to 321 mu mol h(-1), better than that of CZS5/Pt-0.3% sample (134 mu mol h(-1)) under the same conditions. TEM and SEM images show that phosphides were tightly attached to the CdxZn1-xS solid solution by face-to-face orientation contact. UV-vis diffuse reflection spectra and electrochemical characterization demonstrate that binary CZS5/Cu3P-0.3% nanocomposites possessed positive visible-light response, desirable adsorptive capacity and favorable photogenerated charge transfer. The photocatalytic mechanism was further proposed that Cu3P could act as a significant charge acceptor for the enhancement of photogenerated carriers separation and transfer. This work provides a constructive direction for reasonable selection of highly efficient co-catalysts to replace noble metals and expand the application of photocatalytic materials.