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 (29mL/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 0.05M sulfide ion, 0.2M sulfite ion, pH 11.3, and 500mg/L photocatalyst. A final conversion of 30% was achieved under optimized conditions. This is a cleaner production method for generating H-2 and also an environmentally benign process.