Sequential cocatalyst decoration on BaTaO2N towards highly-active Z-scheme water splitting

Oxynitride photocatalysts hold promise for renewable solar hydrogen production via water splitting owing to their intense visible light absorption. Cocatalyst loading is essential for activation of such oxynitride photocatalysts. However, cocatalyst nanoparticles form aggregates and exhibit weak interaction with photocatalysts, which prevents eliciting their intrinsic photocatalytic performance. Here, we demonstrate efficient utilization of photoexcited electrons in a single-crystalline particulate BaTaO 2 N photocatalyst prepared with the assistance of RbCl flux for H 2 evolution reactions via sequential decoration of Pt cocatalyst by impregnation-reduction followed by site-selective photodeposition. The Pt-loaded BaTaO 2 N photocatalyst evolves H 2 over 100 times more efficiently than before, with an apparent quantum yield of 6.8% at the wavelength of 420 nm, from a methanol aqueous solution, and a solar-to-hydrogen energy conversion efficiency of 0.24% in Z-scheme water splitting. Enabling uniform dispersion and intimate contact of cocatalyst nanoparticles on single-crystalline narrow-bandgap particulate photocatalysts is a key to efficient solar-to-chemical energy conversion. Activation of narrow-bandgap photocatalysts holds key to applicable solar-to-hydrogen energy conversion. Here, the authors demonstrate effective sequential cocatalyst decoration for such narrow-bandgap photocatalysts to realise highly-efficient hydrogen evolution and Z-scheme water splitting.