Highly oxidative GaN:ZnO@α-Ga2O3 heterostructure as a visible-light-driven, round-the-clock photocatalyst for dye degradation and disinfection†

Abstract

A significant challenge in the application of photocatalysis in environmental remediation is maintaining high catalytic activity day and night, even during extreme weathers. In this study, a unique round-the-clock GaN:ZnO@α-Ga₂O₃ photocatalyst facilitating the effective separation and simultaneous storage of photogenerated electrons and holes was constructed via the facile post-treatment of soaking segregated wurtzite GaN:ZnO particles in a nonvolatile trihalide ionic liquid of [P₄₄₄₁₀][Br₃], followed by air-annealing. The obtained GaN:ZnO@α-Ga₂O₃ heterostructure facilitated spontaneous generation of reactive oxygen species, including ·OH, ¹O₂ and ·O₂⁻. GaN:ZnO in the heterostructure harvested visible light, stored photoelectrons, and absorbed O₂ at oxygen vacancies (V_O) to produce ·O₂⁻. For the first time, gallium vacancy (V_Ga)-rich α-Ga₂O₃ is proposed as a hole-storage material in this paper. The point defects of V_O and V_Ga in α-Ga₂O₃ played a vital role in absorbing H₂O/O₂ molecules, trapping photogenerated holes, and forming ·OH and ¹O₂. α-Ga₂O₃ is energetically more inclined to adsorb and dissociate H₂O molecules at V_O, forming predominant active species of ·OH owing to the high valence band edge of 3.918 eV, which endowed the photocatalyst with strong oxidizing ability. Consequently, the GaN:ZnO@α-Ga₂O₃ heterostructure exhibited an excellent catalytic performance in the degradation of Rhodamine B (RhB) in solution, even in the dark, and showed high antibacterial activities towards Staphylococcus aureus and Escherichia coli in the dark and under sunlight irradiation. These new findings form a solid basis for the design and fabrication of highly oxidative visible-light-driven photocatalysts for round-the-clock water/air purification.