Enhanced photocatalytic water splitting of hydrous LiCa2Ta3O10 prepared by hydrothermal treatment

Hydration behavior of A'Ca2Ta3O10 (A' = Cs, Rb, K, Na, and Li) was studied focusing on the photocatalytic activity for overall water splitting under UV-irradiation. Interlayer hydration was only observed for A' = Na and Li, which possess a large enthalpy of hydration (Delta H-h degrees). A Na phase readily yielded a stable hydrous phase even at ambient temperature, whereas a Li phase required hydrothermal treatment at >= 160 degrees C. This is consistent with the fact that the Na phase kept its space group (14/mmm) unchanged during hydration, whereas the Li phase changed from 14/mmm to P4/mmm. Hydration of the Li phase doubled the rate of photocatalytic gas evolution ( >= 700 mu mol-H(2)h(-1)) in the presence of 0.5 wt % Ni load, which was the highest in the series of A'Ca2Ta3O10. It was demonstrated that the hydrated interlayer is an efficient structural modification to enhance the photocatalytic activity of the ion-exchangeable layered perovskite-type oxides.