Single-Crystalline LaTiO2N Nanosheets with Regulated Defects for Photocatalytic Overall Water Splitting under Visible Light up to 600 nm

Overall water splitting (OWS), liberating H2 and O2 in a 2:1 ratio, based on powdery photocatalysts, represents a simple and cost-effective means for solar hydrogen production. For an efficient solar energy harvest, the use of OWS reactions should be operated using narrow-band gap semiconductors, which remains a great challenge. In this work, photocatalytic OWS reactions, operable up to 600 nm, have been achieved over a narrow-band gap semiconductor LaTiO2N with single-crystalline nanosheet morphology. These nanosheets, prepared via a topotactic route, are of a low concentration of Ti3+ defects whose locations are limited to the top surface of ∼1 nm thickness. Such a regulated Ti3+ distribution is essential for OWS reactions as it enables the accumulation of both photogenerated electrons and holes at the surface region simultaneously. Compared with conventional inactive LaTiO2N, LaTiO2N single-crystalline nanosheets can stably photocatalyze OWS reactions under visible light and simulated AM1.5G after being deposited with the RhCrOy cocatalyst and coated with a Ti oxyhydroxide layer. These findings provide a rational guideline to open up the OWS activity of narrow-band gap semiconductors by proper defect regulation.