Concurrent Hydrogen Production and Hydrogen Sulfide Decomposition by Solar Photocatalysis.

Core-shell (CdS-ZnS)/TiO₂ nanoparticles (TiO₂ - core, CdS-ZnS − shell) were synthesized and their photocatalytic activity for hydrogen generation was compared with CdS, ZnS, and CdS-ZnS nanoparticles and TiO₂ nanorods. Physical characterization of the catalysts was carried out for particle size, molecular vibrations, band gap energy, specific surface area, and binding energy. Based on the results, core-shell formation between CdS-ZnS and TiO₂ was established. The CdS-ZnS/TiO₂ core-shell NPs exhibited high rates of hydrogen generation (29 mL/h) from water containing sulfide and sulfite ions. Photocatalytic generation of hydrogen with CdS-ZnS/TiO₂ core-shell nanoparticles was investigated by optimizing various operating variables as, e.g., the sulfide ion concentration, sulfite ion concentration, pH, catalyst concentration, light intensity and recycle flow rates in a 1 L laboratory scale tubular photoreactor. The maximum kinetic constant of 0.0038 min⁻¹ was found at 0.05 M sulfide ion, 0.2 M sulfite ion, pH 11.3, and 500 mg/L photocatalyst. A final conversion of 30% was achieved under optimized conditions. This is a cleaner production method for generating H₂ and also an environmentally benign process. [ABSTRACT FROM AUTHOR]