A noticeable improvement of hydrogen production upon photocatalytic water splitting was found recently experimentally on the faceted nanoparticles of strontium titanate (SrTiO3, STO). In this paper, we study experimentally and theoretically the effects of the Al doping on the electronic structure, optical properties, and hydrogen production efficiency. It is demonstrated here that Al doping significantly increases the photoactivity in water splitting. The preparation of Al-doped STO photocatalysts in molten KCl with further optimization of the synthesis procedure and co-catalyst deposition is a cheaper and lower-synthesis-temperature alternative to SrCl2 molten salt system. In turn, the first-principles calculations of the dopant in the bulk and at the surface show that doping does not considerably affect the band gap (in full accordance with our experimental data) but leads to photostimulated mobile hole trapping at local energy levels close to the valence band top which likely prevents the electron–hole recombination and thus stimulated hydrogen reduction.

Photocatalytic water splitting is a promising approach to converting solar energy into green hydrogen. As an effective photocatalyst, Rh x Cr2–x O3/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 x Cr2–x O3, 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 x Cr2–x O3/SrTiO3. Especially Al-doped Rh x Cr2–x O3/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 x Cr2–x O3 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.