Promoting Photocatalytic Overall Water Splitting by Controlled Magnesium Incorporation in SrTiO3 Photocatalysts

SrTiO3 is a well-known photocatalyst inducing overall water splitting when exposed to UV irradiation of wavelengths < 370 nm. However, the apparent quantum efficiency of SrTiO3 is typically low, even when functionalized with nanoparticles of Pt or Ni@NiO. Here, we introduce a simple solid-state preparation method to control the incorporation of magnesium into the perovskite structure of SrTiO3. After deposition of Pt or Ni@NiO, the photocatalytic water-splitting efficiency of the Mg: SrTiOx composites is up to 20 times higher compared to SrTiO3 containing similar catalytic nanoparticles, and an apparent quantum yield (AQY) of 10% can be obtained in the wavelength range of 300-400 nm. Detailed characterization of the Mg: SrTiOx composites revealed that Mg is likely substituting the tetravalent Ti ion, leading to a favorable surface-spacecharge layer. This originates from tuning of the donor density in the cubic SrTiO3 structure by Mg incorporation and enables high oxygen-evolution rates. Nevertheless, interfacing with an appropriate hydrogen evolution catalyst is mandatory and non-trivial to obtain high-performance in water splitting.