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

Abstract

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.