Comparisons of visible-light driven photocatalytic CO₂ conversion performances over mesoporous CdS_xSe_1–x with different molecular compositions

This study presents a synthesis method for nanowire arrayed mesoporous CdS_xSe_1-x compounds with different S/Se molar ratios. Both ternary and binary compound semiconductors are synthesized by hard-templating using SBA-15 as a silica template. The synthesized mesoporous materials have high specific surface areas of approximately 65–100 m² g⁻¹ and remarkable light absorption properties in the UV to visible light region (1.7–2.4 eV), and thus they are appropriate for the photo-conversion of CO₂ into CO and CH₄. The results show that the compositions of CdS_xSe_1-x excellently agree with the compositions of the reactants. Moreover, the band gaps of the mesoporous CdS_xSe_1-x samples could be directly tuned by varying the composition of the reactants. It is concluded that mesoporous CdSe achieves the highest CH₄ yield rate, i.e., 0.382 μmol gcat^–1 h^–1, and CdS_0.5Se_0.5 achieves the highest CO yield rate (among all the samples synthesized), i.e., 5.633 μmol gcat^–1 h^–1. Also, it is found that the CO₂ photoconversion performance on mesoporous II-VI photocatalyst are highly affected by CO₂ adsorption capacities and photo-generated charge separation.