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

Strontium titanium (SrTiO₃) is a promising photocatalyst, but enhancing the separation, migration, and utilization of photocarriers, requires SrTiO₃ with exposed anisotropic facets and minimal defect density. Here, we used NaCl and SrCl₂ as fluxes to synthesize fillet polyhedral SrTiO₃ particles, with Al³⁺ selectively adsorbed as the morphology regulator on high-energy crystal facets. Notably, Al-doped SrTiO₃ synthesized in SrCl₂ 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 SrTiO₃ synthesized in SrCl₂ achieves a hydrogen evolution rate of 255 µmol h^-1, 64 times higher than that of Al-doped SrTiO₃ synthesized in NaCl. Additionally, increasing amounts of cocatalysts further enhances the photocatalytic performance, with the average hydrogen evolution rate of SrTiO₃ 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.