SnO2/SnS2 Heterojunction with Mesoporous Structure for Improved Photocatalytic Degradation of Sulfonamide Antibiotics

Abstract

The SnO₂/SnS₂ composite photocatalyst with mesoporous structure and Type-II heterojunction was successfully constructed, and sulfonamide antibiotics were used as the target degrader to explore the effects of mesoporous and heterojunction structures in SnO₂/SnS₂ on the photocatalytic degradation activity under visible light irradiation. The results show that SnO₂/SnS₂ obtained by hydrothermal reaction at 180 °C presents a unique flower-like spherical structure with high crystallinity and a particle size of about 5 μm, a large mesoporous pore size of 12.33 nm provided abundant ion or molecular channels and a relatively high specific surface area of 50 m²·g^− 1 provided abundant active sites. In addition, SnO₂/SnS₂ has low fluorescence intensity, indicating that the Type-II heterojunction structure formed promoted charge transfer, resulting in a higher separation efficiency of photo-generated charges (h⁺/e⁻). It is worth noting that SnO₂/SnS₂ has a strong light response at the wavelength of 200–800 nm, and degradation rate of SnO₂/SnS₂ was 1.7 times that of SnO₂ and 1.5 times that of SnS₂, after photocatalytic reaction time of 210 min, respectively. It is benefitting from that the Type-II heterojunction structure formed by the coupling of mesoporous SnO₂ and SnS₂ has a synergistic effect, which reduces the band gap and improves the photocatalytic activity. Furthermore, this study revealed that the reaction rate constant of SnO₂/SnS₂ photocatalytic degradation of sulfonamides increased with the increase of temperature, which belonged to the zero-order reaction with the apparent activation energy of \(\:1.201 \times 10^{4}\)J·mol^− 1. Finally, the photocatalytic stability and reusability of SnO₂/SnS₂ were further confirmed through 5 cycles of photocatalytic degradation experiments. This study provides new insights for the development of heterojunction photocatalysts with mesoporous structure, and provide new ideas for photocatalytic technology in antibiotic degradation.

Graphical abstract