Photocatalytic water splitting on Ni-intercalated Ruddlesden-Popper tantalate H2La2/3Ta2O7

A series of Ruddlesden-Popper-type hydrous layered perovskites, A'(2)ATa(2)O(7) (A' = H or K, A = La-2/3 or Sr), were presented as novel catalysts for photocatalytic water splitting into H-2 and O-2 under UV irradiation. These hydrous perovskites showed higher activity than anhydrous perovskites (KTaO3, La1/3TaO3) for overall splitting of water. Results of photoluminescence spectroscopy and H-2 evolution from aqueous n-butylamine solution support the hypothesis that the high activity of the hydrous perovskites results from their hydrated layered structure, where the photogenerated electrons and holes can be effectively transferred to the intercalated substrates (H2O and n-butylamine). Addition of Ni cocatalyst to H2La2/3Ta2O7 via an ion-exchange reaction increased the activity, while Ni addition did not improve the activity of H2SrTa2O7. Ni K-edge EXAFS/XANES, UV-vis spectroscopy, and TEM results for Niloaded catalysts indicate that Ni2+ ions and small NiO clusters are intercalated into the layers of H2La2/3Ta2O7, while relatively large NiO particles at the external surface of the perovskite are the main Ni species in H2SrTa2O7. Thus, the highly dispersed Ni(II) species at the interlayer space are shown to act as effective sites for H-2 evolution in the photocatalytic water splitting.