A stable, efficient and reusable CdS–SnO2 heterostructured photocatalyst for the mineralization of Acid Violet 7 dye

• CdS–SnO2 degrades Acid Violet 7 dye efficiently under sunlight type radiation.
• Not just degradation, but almost complete mineralization of the dye occurs.
• Active species of the degradation reaction are h+, superoxide and hydroxyl radicals.
• This catalyst is found to be stable and reusable.
• Lifetime of the photogenerated charge carriers is more in the composite than in CdS.

We report the photocatalytic activity of a stable and efficient CdS–SnO2 composite for the complete degradation and mineralization of Acid Violet 7 (AV 7, 50 ppm) dye. The composite catalyst exhibits higher photocatalytic activity compared to pure CdS and SnO2. Fluorescence lifetime study shows that the photogenerated charge carriers have higher lifetime in the composite than that in single phase CdS. The enhanced photocatalytic activity is attributed to the increased lifetime of the photogenerated charge carriers in the heterostructured CdS–SnO2 catalyst. Total organic carbon (TOC) analysis indicates that there is hardly any organic carbon in the solution after irradiation for 150 min. Characterization of the catalyst before and after photocatalysis does not show the presence of dye in it in the adsorbed form, suggesting complete mineralization of the dye by the photocatalytic reaction. Experiments with different quenchers indicate that photogenerated holes (h+), superoxide radical anions (O2−) and hydroxyl radicals (OH) play significant roles in the degradation reaction. The composite catalyst exhibits good photo stability and there is no significant deterioration of the catalyst up to 6 cycles of photocatalytic reaction. Present study provides insights for improving the photocatalytic activity and stability of CdS photocatalyst.

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