Novel Zn_0.8Cd_0.2S@g-C₃N₄ core-shell heterojunctions with a twin structure for enhanced visible-light-driven photocatalytic hydrogen generation

A series of novel core-shell nanocomposites composed of twinned nanocrystal Zn_0.8Cd_0.2S solid solution and porous g-C₃N₄ nanosheets were fabricated by a combined ultrasonication and solvothermal method. The photocatalytic hydrogen production activities of these samples were evaluated without a co-catalyst in water under visible light irradiation (λ ≥ 420 nm). It is found that the H₂ production rate of the Zn_0.8Cd_0.2S@g-C₃N₄-10 wt% sample was 2351.18 μmol h^-1 g^-1, which is 146.0 and 5.7 times higher than that of pristine porous g-C₃N₄ nanosheets and Zn_0.8Cd_0.2S solid solution. Further detailed characterization reveals that the drastically enhanced and stable light-to-hydrogen energy conversion can be attributed to not only the efficient spatial separation of the photo-induced electrons and holes resulted from the synergetic effects of twinned homojunctions and core-shell heterojunctions, but also the intimate contact at the molecular scale between the porous g-C₃N₄ shell and Zn_0.8Cd_0.2S core. Therefore, this work puts forward a promising way to obtain unique core-shell heterojunctions with excellent stability and activity during a photoreaction process.