Phase Transition of Two-Dimensional β-Ga(2)O(3) Nanosheets from Ultrathin γ-Ga(2)O(3) Nanosheets and Their Photocatalytic Hydrogen Evolution Activities.

Monoclinic β-Ga(2)O(3) nanosheets hold great potential applications in electronic, optical, and photocatalytic fields. In this study, two-dimensional β-Ga(2)O(3) nanosheets were successfully fabricated through a simple crystalline phase transition from the as-prepared ultrathin γ-Ga(2)O(3) nanosheets. The photocatalytic hydrogen evolution reaction under UV light irradiation was achieved on the two kinds of photocatalysts. However, β-Ga(2)O(3) with a higher crystallinity shows a lower photocatalytic activity in comparison with γ-Ga(2)O(3). The average apparent quantum yield is calculated to be 0.29% for β-Ga(2)O(3) nanosheets and 1.82% for γ-Ga(2)O(3). More efficient separation and transfer rates of photogenerated carriers and larger specific areas were found in γ-Ga(2)O(3). On the basis of the analysis of the structures of γ-Ga(2)O(3) and β-Ga(2)O(3), 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.