Ultrathin Lanthanum Tantalate Perovskite Nanosheets Modified by Nitrogen Doping for Efficient Photocatalytic Water Splitting

Ultrathin nitrogen-doped perovskite nanosheets LaTa₂O_6.77N_0.15^- have been fabricated by exfoliating Dion-Jacobson-type layered perovskite RbLaTa₂O_6.77N_0.15. These nanosheets demonstrate superior photocatalytic activities for water splitting into hydrogen and oxygen and remain active with photon wavelengths as far as 600 nm. Their apparent quantum efficiency under visible-light illumination (λ ≥ 420 nm) approaches 1.29% and 3.27% for photocatalytic hydrogen and oxygen production, being almost 4-fold and 8-fold higher than bulk RbLaTa₂O_6.77N_0.15. Their outstanding performance likely stems from their tiny thickness (single perovskite slab) that essentially removes bulk charge diffusion steps and extends the lifetime of photogenerated charges. Theoretical calculations reveal a peculiar 2D charge transportation phenomenon in RbLaTa₂O_6.77N_0.15; thus, exfoliating RbLaTa₂O_6.77N_0.15 into LaTa₂O_6.77N_0.15^- nanosheets has limited impact on charge transportation properties but significantly enhances the surface areas which contributes to more reaction sites.