The Synergistic Effect of Chlorine Doping and Oxygen Vacancies over SnO2 Photocatalysts for Effectively Degrading Methyl Orange

Abstract

The wide bandgap of SnO₂ photocatalyst limits its application in the field of solar photocatalysis. In this article, it is proposed to introduce oxygen vacancies and Cl ion doping to synergistically enhance the photocatalytic activity of SnO₂ degradation of MO under solar irradiation. This article describes the rapid preparation of efficient SnO₂ photocatalysts through a simple solid-phase reaction method, utilizing SnCl₂·2H₂O and hydrogen peroxide disinfectant (with H₂O₂ as the reactive substance) powder as raw materials. The physicochemical properties of the synthesized SnO₂ were investigated using powder X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Diffuse Reflectance Spectroscopy (DRS), and Photoluminescence (PL), et al. The results indicate that the mixture of SnCl₂·2H₂O and H₂O₂ reacted rapidly to form SnO₂ after simple stirring for more than ten times. XRD analysis revealed the formation of amorphous SnO₂. SEM and TEM results demonstrated that the samples consisted of numerous nanocrystalline grains with an average size of 10 nm. FT-IR results indicated the presence of abundant hydroxyl groups in the samples. XPS characterization confirmed the presence of many hydroxyl groups, oxygen vacancies and small amounts of Cl ion doping in SnO₂. DRS results showed that the synthesized SnO₂ samples exhibited good light absorption capabilities in the visible light region. Additionally, compared to the bandgap width of SnO₂ reagent, the bandgap width of the synthesized samples significantly decreased. The bandgap value of SnO₂ reagent was as high as 3.64 eV. That of the sample with the best performance obtained after optimizing the raw material ratio decreased to 2.52 eV. Its specific surface area reached 149.4 m²/g. The PL results indicate the presence of a great amount of oxygen vacancies in the synthesized SnO₂ sample. At the same time, it can suppress the recombination of photo generated electron hole pairs and improve the separation efficiency of photo generated charge carriers. The prepared SnO₂ photocatalyst demonstrated excellent photocatalytic degradation capabilities. Under simulated sunlight irradiation, the sample with the best performance can completely degrade methyl orange within 6 min. The superior degradation activity towards dyes can be attributed to the extremely fine grain size of the SnO₂ photocatalyst, as well as the synergistic effect of oxygen vacancies and Cl ion doping.