Synthesis of Cd1−xZnxS photocatalysts for gas-phase CO2 reduction under visible light.

Novel photocatalysts for CO₂ reduction, which consist of a cadmium and zinc sulfide solid solution (Cd_1−xZn_xS), were successfully prepared by a simple two-step technique. The photocatalysts were characterized by X-ray diffraction, UV-VIS diffuse reflectance spectroscopy, and low-temperature N₂ adsorption techniques and were tested in the gas-phase photocatalytic reduction of CO₂ under visible light (λ = 450 nm). All the synthesized Cd_1−xZn_xS solid solutions were capable of enabling the chemical transformations of CO₂ under the conditions considered. Carbon monoxide was the major product during the CO₂ reduction over Cd_1−xZn_xS (x = 0–0.87). Methane and hydrogen were also detected in the gas phase in low amounts. The activity of the prepared samples and the distribution of the reduction products strongly depended on the actual cadmium to zinc ratio. The Cd_0.94Zn_0.06S photocatalyst showed the highest activity, 2.9 μmol CO per gram per hour, and selectivity, 95%, during CO₂ reduction under visible light in the presence of water vapor. The achieved values are very high for the sulfide-based photocatalysts. [ABSTRACT FROM AUTHOR]