Photocatalytic degradation of methyl orange by Ca doped β-In₂S₃ with varying Ca concentration

Industrial wastewater is becoming a universal environmental problem, wherein toxic organic compounds are important sources of pollution. For the degradation toxic organic compounds, semiconductor-based photocatalysis has attracted wide attentions due to their photo-electric properties and high efficiency. Due to lots of advantages of β-In₂S₃ and the promotion role of Ca-doped on the photocatalytic performance, the photocatalytic degradation of methyl orange by Ca doped β-In₂S₃ with varying Ca concentration were investigated. The results showed that calcium ion mainly entered into the crystalline lattices of β-In₂S₃ and the addition of Ca has changed the band structure of In₂S₃. The Ca_0.8-β-In₂S₃ had a more abundant lamellar morphology and greater specific surface area than other Ca-doped β-In₂S₃. The increase in the adsorption sites and photocatalytic reaction sites, allowing Ca_0.8-β-In₂S₃ to show the highest photocatalytic activity, which could degrade 98.37% of Methyl Orange (MO) in just 30 min. The improved photocatalytic performance of Ca_0.8-β-In₂S₃ was also owed to the stronger visible light absorption, narrower band gap (2.16 eV), and photogenerated the effective separation of electron–hole pairs (e⁻/h⁺). When the light was shone onto the surface of Ca_0.8-β-In₂S₃, more charge carriers and ·O₂⁻ were excited because Ca_0.8-β-In₂S₃ had a narrower band gap and lower CB position. Additionally, h⁺ played a dominant role on the photocatalytic degradation of MO. Furthermore, the optimized Ca_0.8-β-In₂S₃ photocatalyst had excellent stability and recoverability, which would be greatly helpful for practical application. The present work demonstrated that the optimal doping amount of Ca-doped β-In₂S₃ was 5.8%, which provides a favorable guideline for the further application of Ca-doped β-In₂S₃ to degrade pollutants.