Effect of the composition ratio of ZnO/Zn₂SnO₄ composite on its visible photocatalytic activities in the photodegradation of methylene blue and rhodamine B organic dyes

Abstract Photocatalysis is an effective solution for wastewater treatment problems, and semiconductor heterojunctions for photocatalysis can effectively separate photogenerated carriers to improve the photocatalytic degradation efficiency of pollutants. In this study, a heterojunction photocatalyst with a ZnO/Zn 2 SnO 4 composite structure was fabricated to degrade methylene blue (MB) and rhodamine B (RhB) dyes using visible light. The crystal structure, size, chemical composition, valence state, vibrational modes, and chemical composition of the ZnO/Zn 2 SnO 4 photocatalyst were analyzed by XRD, TEM, EDX, XPS, and Raman spectroscopy. The absorption properties, band gap, and photoluminescence properties investigated by UV–Vis absorption and photoluminescence spectra. In addition, the photodegradation mechanism and charge transfer of the ZnO/Zn 2 SnO 4 heterostructure were analyzed in detail. The ZnO/Zn 2 SnO 4 composites showed the characteristic peaks of ZnO and Zn 2 SnO 4 , proving the formation of their heterostructure. In the photodegradation experiment under visible light, the ZS80 sample exhibited the best photocatalytic degradation performance of 93.11% for MB and 97.13% for RhB after 120 min of lighting. In addition, the ZnO/Zn 2 SnO 4 composites showed an increase in the lifetime of the photogenerated charged carriers and a decrease in the recombination of photogenerated electron–hole pairs. Its heterostructure effectively inhibited electron–hole recombination, remarkably improved the activity and stability of the catalyst, and promoted the catalytic reaction efficiency. The superior photodegradation performance of the heterostructure makes it applicable in the degradation of environmental pollutants.