Photocatalytic hydrogen generation with simultaneous organic degradation by a visible light-driven CdS/ZnS film catalyst

A layered CdS/ZnS catalyst film was synthesized on glass using the stepped chemical bath deposition method. The film catalyst was shown as visible light-driven photocatalyst capable of producing H-2 under visible light. The ZnS outer layer helped suppress the recombination of photo-generated electron-hole pairs on the CdS base layer, leading to faster H-2 generation. The use of the ZnS layer also greatly improved the stability of the catalyst film and prevented the leaching of Cd2+ from the CdS layer. Deposition of Ru on the catalyst film further increased its photoreactivity for H-2 production. The photocatalyst was effective in H-2 production together with the degradation of model organic substances, such as formic acid, methanol, and ethanol. The greatest H-2 production rates were achieved using the CdS/ZnS/Ru film in the formic acid solution at 123 mu mol/m(2)-h under visible light and 135 mmol/m(2)-h under the simulated solar light. The corresponding theoretical reduction rates of chemical oxygen demand (COD) were 1.9 and 2.1 g/m(2)-h, respectively. As the multilayer CdS/ZnS/Ru film catalyst can be easily separated from water, it has a great potential for simultaneous photocatalytic hydrogen generation and organic wastewater treatment using solar energy. (C) 2013 Elsevier B.V. All rights reserved.