Effect of Ga2O3 Crystal Phase on Photocatalytic Degradation of Perfluorooctanoic Acid

Abstract

In this study, we systematically investigated the effects of the crystal phase (α, β, and γ) and crystallinity of Ga₂O₃ on the photocatalytic degradation activity toward perfluorooctanoic acid (PFOA). Among the tested catalysts, β-Ga₂O₃ exhibited the highest degradation activity, and even within the same β phase, the activity varied markedly depending on the crystallinity. Degradation experiments using various scavengers showed that the reaction proceeds predominantly via direct oxidation by photogenerated holes, while ∙OH radicals contribute very little to the degradation. The superior activity of highly crystalline β-Ga₂O₃ is attributed to synergistic effects of suppressed charge-carrier recombination, improved hole-utilization efficiency associated with a relatively low amount of surface hydroxyl groups, and a surface coordination environment favorable for substrate adsorption. These findings demonstrate that controlling crystal structure and crystallinity is crucial for improving the performance of Ga₂O₃ photocatalysts for PFOA degradation.