Effects of Al Doping on Hydrogen Production Efficiency upon Photostimulated Water Splitting on SrTiO3 Nanoparticles

A noticeable improvement of hydrogen production upon photo-catalytic 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.