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

Abstract

A tough challenge for photocatalysis applied in environmental remediation is the maintenance of a high catalytic activity day and night or through the broken weather. In this study, an unique round-the-clock GaN:ZnO@α-Ga₂O₃ photocatalyst capable of effective separation and simultaneous storage of photogenerated electrons and holes was constructed by facile post-treatments 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 allowed a spontaneous generation of reactive oxygen species including •OH, ¹O₂ and •O₂⁻. The 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, the gallium vacancy (V_Ga)-rich α-Ga₂O₃ was proposed as a hole-storage material in this paper. The point defects of V_O and V_Ga in the α-Ga₂O₃ played a vital role in absorbing H₂O/O₂ molecules, trapping photogenerated holes, and forming •OH and ¹O₂. The α-Ga₂O₃ is energetically more inclined to adsorb and dissociate H2O molecules at VO, leading to a predominant active species of •OH due to the high valence band edge of 3.918 eV, which endowed the photocatalyst with a strong oxidizing ability. The GaN:ZnO@α-Ga₂O₃ heterostructure exhibited an excellent catalytic performance to degrade Rhodamine B (RhB) in the solution even in the darkness, and showed high antibacterial activities towards Staphylococcus aureus and Escherichia coli in the dark and under the sun-light irradiation as well. These new findings form a solid base to design and fabricate a highly oxidative visible-light-driven photocatalyst for round-the-clock water/air purification.