| Abstract
| - The first example of an active layered tantalate photocatalyst containing partly filledlanthanide 4f shell is reported. A single phase of layered perovskite tantalates, RbLnTa2O7,could be obtained with Ln = La, Pr, Nd, and Sm; the ionic radii of these trivalent cationsare required to be larger than 0.126 nm for constructing a perovskite slab. Under UVirradiation from a high-pressure Hg lamp, these layered tantalates demonstrated thephotocatalytic activity for water splitting into stoichiometric H2/O2 mixtures even withoutloading metal catalysts. The rates of H2 and O2 evolutions were found to be stronglydependent on the lanthanoids, increasing in the sequence of La ≑ Pr ≪ Sm < Nd. Themaximum rate of H2 evolution observed over RbNdTa2O7 reached 47.0 μmol/h. The absorptionspectrum of RbNdTa2O7 consists of the internal 4f transitions in the visible region and abroad band overlapping the band-gap transition in the UV region. The latter band indicatesthat a possible excitation process including the partly filled 4f shell plays a key role inphotocatalytic reactions. Loading 0.5 wt % Ni onto RbNdTa2O7 by simple impregnationsignificantly improved H2 evolution (117.2 μmol/h).
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