Activation of hydrogen-evolution reactivity in an Rh-doped SrTiO3 photocatalyst under visible-light irradiation by loading with controlled platinum nanoclusters

Abstract

Rhodium-doped strontium titanate (SrTiO₃:Rh)-based photocatalysts have long been studied because they can produce hydrogen (H₂) from visible light and water in Z-scheme water-splitting systems. However, the H₂-evolution reaction (HER) of SrTiO₃:Rh is the rate-limiting step in such a system, so further improvement of the HER activity of SrTiO₃:Rh is desired to enhance Z-scheme water splitting. In this study, we synthesize hydrophilic ∼1 nm platinum nanoclusters (Pt NCs) using a ligand-exchange method while maintaining the geometric structure of the corresponding hydrophobic ∼1 nm Pt NC, and we load the monodispersed Pt NCs onto SrTiO₃:Rh. The Pt NC-loaded SrTiO₃:Rh exhibits HER activity that is 30% higher than that of the Pt cocatalyst-loaded SrTiO₃:Rh prepared using the conventional photodeposition method. This work also demonstrates that Z-scheme water splitting proceeds stoichiometrically using the Pt NC-loaded SrTiO₃:Rh as the H₂-evolution photocatalyst, bismuth vanadate as an oxygen-evolution photocatalyst, and Fe²⁺ as a mediator.