Phase Transition of Two-Dimensional β-Ga₂O₃ Nanosheets from Ultrathin γ-Ga₂O₃ Nanosheets and Their Photocatalytic Hydrogen Evolution Activities

Abstract

Monoclinic β-Ga₂O₃ nanosheets hold great potential applications in electronic, optical, and photocatalytic fields. In this study, two-dimensional β-Ga₂O₃ nanosheets were successfully fabricated through a simple crystalline phase transition from the as-prepared ultrathin γ-Ga₂O₃ nanosheets. The photocatalytic hydrogen evolution reaction under UV light irradiation was achieved on the two kinds of photocatalysts. However, β-Ga₂O₃ with a higher crystallinity shows a lower photocatalytic activity in comparison with γ-Ga₂O₃. The average apparent quantum yield is calculated to be 0.29% for β-Ga₂O₃ nanosheets and 1.82% for γ-Ga₂O₃. More efficient separation and transfer rates of photogenerated carriers and larger specific areas were found in γ-Ga₂O₃. On the basis of the analysis of the structures of γ-Ga₂O₃ and β-Ga₂O₃, it is proposed that the disordered or defective structure contributes to the improvement of photocatalytic activity to some extent. Therefore, it is significant to develop the photocatalyst with a stable structure and a certain number of defects at the same time.