CuGaS2 Quantum Dots on the Hollow Spheres of TiO2 as S-Scheme Heterostructures for Efficient Photocatalytic Degradation of Methyl Orange

Abstract Photocatalysis is a promising method for treating organic pollutants. However, the wide band gap of TiO2 limits its photocatalytic performance. In this study, CuGaS2 quantum dots (QDs) were grown in situ on TiO2 hollow spheres to construct a heterojunction for methyl orange (MO) removal. The composite with 10 wt % CuGaS2 showed the best performance. It removed 95.72% of MO within 30 min under UV irradiation (k = 0.1031 min−1), which was 1.6 and 11.1 times higher than those of TiO2 and CuGaS2 QDs, respectively. The catalytic performance remains stable over repeated cycling. In addition, radical scavenging experiments and band structure analysis confirm an S-scheme mechanism.