Engaging the flux-grown La_1−xSr_xFe_1−yTi_yO₃ crystals in visible-light-driven photocatalytic hydrogen generation

Perovskite LaFeO₃ is regarded as one of the promising photocatalysts for solar splitting of water to hydrogen and oxygen due to its suitable band edge positions, visible light absorbance, and high chemical stability. To further improve its photocatalytic performance of LaFeO₃, the effects of solute concentration in the KCl-flux growth and partial A– and B–site substitution are investigated in this work. Controlling the solute concentration in the range of 1–20 mol% is crucial to grow phase-pure LaFeO₃ crystals with idiomorphic shape. With increasing the solute concentration, the flux-based growth route gradually changes to a solid state-based growth route because of a decrease in solubility and an increase in the crystallization core number. The La_1−xSr_xFe_1−yTi_yO₃ (x,y = 0,0; 0,0.15; 0.15,0; 0.1125,0.0375; 0.0375,0.1125; and 0.075,0.075) crystals were also synthesized by a KCl-flux method to explore the effect of partial Sr²⁺-to-La³⁺ and/or Ti⁴⁺-to-Fe²⁻⁴⁺ substitution on photocatalytic performance of LaFeO₃. The Sr²⁺–Ti⁴⁺ co-substitution is found to enhance the photocatalytic performance of LaFeO₃ as compared with the corresponding individual substitution (Sr²⁺ or Ti⁴⁺). The highest photocatalytic hydrogen generation rate (83.2 μmol h⁻¹) was observed for Pt-photodeposited La_0.925Sr_0.075Fe_0.925Ti_0.075O₃ crystals in 5-h reaction due to the improvement of both bulk properties and photoactivity and the reduction in both grain boundaries and lattice defects stemmed from the Sr²⁺–Ti⁴⁺ co-substitution and KCl flux growth.