Photocatalytic Water Splitting of Al-Doped RhxCr2-xO3/SrTiO3 Synthesized by Flux Method: Elucidating the Role of Different Molten Salts

Photocatalytic water splitting is a promising approach to converting solar energy into green hydrogen. As an effective photocatalyst, Rh_xCr_2-xO₃/SrTiO₃ has been widely studied for water splitting, mainly synthesized using SrCl₂ molten salt as the reaction media. This research systematically studied the effect of molten salts and Al doping in order to test and integrate the combinatorial effect of the modifications of SrTiO₃-based catalysts. A series of SrTiO₃ and Al-doped SrTiO₃ (Al:SrTiO₃) were synthesized by the flux method with three molten salts (NaCl, KCl, and SrCl₂·6H₂O) at different annealing temperatures (900 and 1000 °C). Cocatalyst, Rh_xCr_2-xO₃, was loaded on the surface of Al-doped SrTiO₃ by impregnation and photodeposition methods for comparison. The photocatalytic performance of overall water splitting was evaluated in pure water under UV and AM 1.5G simulated sunlight. A significant improvement in photocatalytic activity was observed in Al-doped Rh_xCr_2-xO₃/SrTiO₃. Especially Al-doped Rh_xCr_2-xO₃/SrTiO₃ synthesized by KCl molten salt showed the highest hydrogen evolution rate with the synergy effect of molten salt and Al doping. Furthermore, hydrogen evolution rates were further enhanced by loading core-shell Rh_xCr_2-xO₃ using in situ photodeposition instead of impregnation, reaching 784 and 431 μmol h^-1 g^-1 H₂ under 365 nm UV light and AM 1.5G irradiation, respectively.