Effect of Different Molten Salts on Structure and Water Splitting Performance of Al‐Doped Fillet Polyhedral SrTiO3

Abstract Strontium titanium (SrTiO 3 ) is a promising photocatalyst, but enhancing the separation, migration, and utilization of photocarriers, requires SrTiO 3 with exposed anisotropic facets and minimal defect density. Here, we used NaCl and SrCl 2 as fluxes to synthesize fillet polyhedral SrTiO 3 particles, with Al 3+ selectively adsorbed as the morphology regulator on high‐energy crystal facets. Notably, Al‐doped SrTiO 3 synthesized in SrCl 2 exhibits regular polyhedral morphology with {100}, {110}, and high‐index {112} facets, showing high surface activity, low internal defect density, and superior photocatalytic performance. The excellent performance is attributed to the spatial separation of photocarriers on different crystal facets. In situ photodeposition experiments confirmed that photogenerated electrons were concentrated on the {100} facets, while holes were concentrated on the {110} and {112} facets, effectively impeding recombination. After loading RhCrO x /CoO x , Al‐doped SrTiO 3 synthesized in SrCl 2 achieves a hydrogen evolution rate of 255 µmol h −1 , 64 times higher than that of Al‐doped SrTiO 3 synthesized in NaCl. Additionally, increasing amounts of cocatalysts further enhances the photocatalytic performance, with the average hydrogen evolution rate of SrTiO 3 reaching 319 µmol h⁻¹, an apparent quantum yield of 3.5% at 365 nm, and a solar‐to‐ hydrogen value of 0.181%. This discovery offers new insights into designing efficient photocatalysts for hydrogen production.