Preparation of Ga2O3/ZnO/WO3 double S-scheme heterojunction composite nanofibers by electrospinning method for enhancing photocatalytic activity

Abstract

Ga2O3 is a semiconductor material with ultra-wide band gap (Eg = 4.9 eV), which has photocatalytic activity only under deep ultraviolet light irradiation (λ < 258 nm). In this study, Ga2O3/ZnO/WO3 double S-scheme heterojunction composite nanofibers were prepared by electrospinning method. The results show that the composite nanofibers have strong photocatalytic activity and sensitive response under UV–visible light irradiation. According to the heterojunction energy band matching theory of S-scheme, the photogenerated electrons (e−) of Ga2O3, ZnO, and WO3 are transferred from the valence band (VB) to the conduction band (CB), and photogenerated holes (h+) are generated in VB under the UV–visible light irradiation with sufficient energy. These factors (the internal electric field, band bending, and Coulomb attraction) are the driving forces to promote the useless e− and h+ are eliminated through recombination. Consequently, the powerful e− with strong reducing ability in the CB of Ga2O3 and the h+ with strong oxidizing ability in the VB of WO3 are preserved to engage in photocatalytic reactions. With Rhodamine B (Rh B) dye as the degradation target, the degradation efficiency of WO3, ZnO/WO3, and Ga2O3/ZnO/WO3 nanofibers were measured under UV–visible light irradiation for 120 min. The experimental results show that compared with WO3 and ZnO/WO3 nanofibers, Ga2O3/ZnO/WO3 composite nanofibers have the highest photocatalytic activity and excellent redox ability as photocatalyst. Besides, the response range of Ga2O3/ZnO/WO3 to the ultraviolet–visible spectrum is greatly expanded.