Preparation of tantalum-based oxynitride nanosheets by exfoliation of a layered oxynitride, CsCa2Ta3O(10-x)N(y), and their photocatalytic activity.

Calcium tantalum oxynitride [Ca(2)Ta(3)O(9.7)N(0.2)](-) nanosheets were prepared by exfoliating a layered perovskite oxynitride (CsCa(2)Ta(3)O(9.7)N(0.2)) via proton exchange and two-step intercalation of ethylamine and tetrabutylammonium ions. Monolayer nanosheet was prepared by the above processes, although some bilayer or trilayer nanosheets were also produced. The [Ca(2)Ta(3)O(9.7)N(0.2)](-) nanosheets exhibited photocatalytic activity for H(2) evolution from water under visible light irradiation. In contrast, CsCa(2)Ta(3)O(9.7)N(0.2) exhibited very low photocatalytic activity for H(2) evolution under the visible light irradiation, even when methanol was added to water as a sacrificial agent. The improved photocatalytic activity originates from the characteristics of nanosheets such as their molecular thickness and large surface area. Further, the Rh-loaded [Ca(2)Ta(3)O(9.7)N(0.2)](-) nanosheets restacked with protons exhibited photocatalytic activity for H(2) and O(2) evolution from pure water under UV-light irradiation. The ratio of H(2)/O(2) evolved was around 3. The ratio of N/O in the catalyst remained the same after the photocatalytic reaction, signifying that there was no decomposition of the catalyst during the reaction. This indicates that the present N-doped nanosheet is stable in the photocatalytic reaction.