Black strontium titanate nanocrystals of enhanced solar absorption for photocatalysis

Black titania has attracted enormous attention due to its enhanced photocatalytic activity via increased solar absorption, but few studies extended the investigations to other wide band-gap titanates. Herein, strontium titanate (SrTiO₃), a typical ternary titanate with more potential in photocatalysis, is selected as the target material. Black SrTiO₃ nanocrystals were obtained by molten aluminum reduction of solution-processed pristine SrTiO₃ in a two-zone furnace. Different from the black titania, black SrTiO₃ nanocrystals are well-crystallized and have no core-shell structure. Substantial Ti³⁺ cations and oxygen vacancies are introduced into SrTiO₃ after aluminum reduction, which results in enhanced absorption in both visible and near-infrared regions, and improved charge separation and transport. The photocatalytic hydrogen-generation and photoelectrochemical investigations demonstrate that black SrTiO₃ exhibits an impressive improvement (2.5 times and 2.4 times at 1.23 V_RHE, respectively) compared with white SrTiO₃.