An efficient particulate photocatalyst for overall water splitting based on scandium and magnesium co-doped strontium titanate

Effects of co-doping of aluminum (Al), scandium (Sc), and magnesium (Mg) into SrTiO3 particles by a high temperature (1200 °C) flux treatment in a molten SrCl2 on the structural properties and photocatalytic activities for overall water splitting were investigated. Isotropically-rounded polygonal-shaped particles of almost phase-pure SrTiO3 crystals were obtained from SrTiO3 particles co-doped with Al and Sc (SrTiO3:Al,Sc) and Al and Mg (SrTiO3:Al,Mg), whereas, the cubic-shaped particles having specific nanosized steps on the edge of each particle were obtained by co-doping with Sc and Mg (SrTiO3:Sc,Mg). Apparent quantum yields (AQYs) for overall water splitting at a band edge region (365 nm) were examined using these SrTiO3 samples loaded with Rh/Cr2O3 and CoOOH cocatalyst nanoparticles (for H2 and O2 evolution, respectively), and it reached the highest (66%) when the photocatalyst based on SrTiO3:Sc,Mg was used. The best photocatalytic performance obtained over the photocatalyst is attributed to the achievement of the separation of reaction sites for reduction and oxidation of water, i.e., the former reaction occurred on the Rh/Cr2O3 cocatalyst selectively deposited on the flat {100} facets of the SrTiO3:Sc,Mg particle, whereas the later O2 evolution occurred on the CoOOH cocatalyst that was only deposited on the nanosized step part on the particle.