Effect of annealing temperature on the formation of oxygen vacancies on the surface of flower-like SnSe/SnO2 heterostructure and visible light catalytic performance

Abstract

The morphology, structure, and oxygen vacancies in principle determine the light absorption, charge transfer, and separation of photocatalysts, thereby determining their photocatalytic performance. In this study, flower-like SnSe obtained from hydrothermal reactions was oxidized to obtain heterojunctions with SnSe/SnO2. Flower-like SnSe/SnO2 heterojunctions with different concentrations of oxygen vacancies were prepared by annealing them in an argon atmosphere at different temperatures. The flower-like SnSe/SnO2 series with different oxygen vacancies were systematically characterized by TEM, XRD, XPS, PL, and EPR. The research results demonstrate the presence of oxygen vacancies in the flower-like SnSe/SnO2. As the annealing temperature increases, the surface oxygen vacancy concentration shows a trend of first increasing and then decreasing. When the annealing temperature reaches 600 °C, the oxygen vacancy concentration of flower-like SnSe/SnO2 is the highest. Meanwhile, research has shown that surface oxygen vacancies help expand the light absorption range, and the increased valence bandwidth leads to effective charge transfer and separation, thereby promoting visible light photoactivity. SnSe/SnO2-600 °C exhibited excellent visible light photocatalytic activity. The photodegradation of methylene blue (MB) at ≥ 400 nm can reach ∼70% within 120 min. This study verified the route for the introduction of oxygen vacancies via facile calcination and constructed SnSe/SnO2 with surface oxygen vacancies, providing a reference with deep insights for improving photocatalytic activity.