Photocatalytic Reduction of CO2 Over CdS, ZnS and Core/Shell CdS/ZnS Nanoparticles Deposited on Montmorillonite

CdS, ZnS and core/shell CdS/ZnS nanoparticles deposited on montmorillonite (MMT) were synthesized by one-pot procedure, that is, by subsequent precipitation of CdS and ZnS nanoparticles in one aqueous dispersion of cetyltrimethylammonium bromide (CTAB) and deposited on montmorillonite. The prepared nanoparticles were characterized by chemical analysis, N-2 physisorption measurements, UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), temperature programmed desorption (TPD) of CO2 and high resolution transmission electron microscopy (HRTEM). The photocatalytic performance of these materials was investigated for the H-2 and CH4 evolution from the CO2 reduction in water media under UV irradiation (lambda = 254 nm and 365 nm). The control experiment was carried out to guarantee that the product was produced by CO2 photocatalytic reduction. The key role in activity of the core/shell photocatalysts was played by the photogenerated electrons and holes in ZnS which could change over to valence and conductivity bands of CdS and could react with hydrogen cations to create hydrogen. Increase of the core/shell photocatalytic activity could be caused by increase of specific surface area, inhibition of CdS photocorrosion and surface electronic state passivation of CdS cores by ZnS shells.