A facile two-step method to synthesize immobilized CdS/BiOCl film photocatalysts with enhanced photocatalytic activities

Immobilized CdS/BiOCl film photocatalysts were successfully synthesized by a facile two-step hydrothermal-hydrolysis method. The structures, morphologies, photocatalytic properties and reusabilities of the samples were studied. The photocatalytic activities of CdS/BiOCl were significantly improved compared with pure BiOCl. The photocatalytic activity of 6% CdS/BiOCl was the highest and 10 times higher than pure BiOCl, which was attributed to the enhanced visible light absorption and the higher separation of photogenerated carriers. Besides, 6% CdS/BiOCl also showed good recycling performance. A new photocatalytic mechanism, totally different from other mechanisms of BiOCl-based heterostructures, was revealed. It was part of electrons on the conducting band of CdS rather than the transferred electrons on the conducting band of BiOCl that oxidized O₂ into O₂⁻, and O₂⁻ together with h⁺ on the valence band of CdS degraded organic pollutants. BiOCl did not generate electrons and holes, but only served as the electron transferer as electrons on the conducting band of CdS transferred to the conducting band of BiOCl, facilitating the separation of hole-electron pairs. This work provided a good reference for design and synthesis of film photocatalysts and new insights into photocatalytic mechanisms for heterostructures.