Investigation on the highly active SrTiO₃ photocatalyst toward overall H₂O splitting by doping Na ion

Photocatalytic properties of SrTiO₃ doped with Na ion (Na⁺-SrTiO₃) were investigated to develop the photocatalyst exhibiting high photocatalytic performances, not only the activity but also the durability for overall H₂O splitting. The photocatalytic activity was remarkably improved by the introduction of a small amount of Na ion into SrTiO₃ photocatalyst using rhodium and chromium mixed oxide (Rh_0.7Cr_1.3O₃) as the co-catalyst. Moreover, the photocatalytic activity was influenced by the purity of the raw materials used for preparing Na⁺-SrTiO₃ photocatalyst rather than the properties that originated with the preparation methods. The apparent quantum yield (AQY) of overall H₂O splitting was 28% under the irradiation at 365 nm over the optimal Rh_0.7Cr_1.3O₃/Na⁺-SrTiO₃ photocatalyst. The photocatalytic performances of Rh_2-yCr_yO₃/Na⁺-SrTiO₃ were confirmed to be further improved by separating the hydrogen evolution reaction (HER) site and the oxygen evolution reaction (OER) site over the surface by co-loading CoO_x co-catalyst as OER sites. The states of Na⁺ doped SrTiO₃ was investigated to make clear the key factors in the enhancement of the photocatalytic activity by the doping of aliovalent ions.