Visible-light-driven photocatalysis via reductant-to-band charge transfer in Cr(III) nanocluster-loaded SrTiO3 system

Designing efficient visible-light-active photocatalysts is important for practical uses. Herein, strontium titanate (SrTiO3), a wide-bandgap semiconductor, loaded with chromium (III) nanoclusters has been demonstrated as a visible-light-active photocatalyst driven by the reductant-to-band charge transfer (RBCT) mechanism. The action spectrum revealed that absorption at around 430 nm contributed considerably to the photocatalytic 2-propanol decomposition. The reaction mechanism in the Cr(III)-loaded SrTiO3 system was studied by electron spin resonance (ESR) spectroscopy, electrochemical, and photoelectrochemical technique. We confirmed that the interfacial electron transfer (i.e., RBCT) from Cr(III) nanoclusters to the conduction band of SrTiO3 initiated the photocatalytic reaction under visible-light irradiation. In this system, moreover, the Cr(III) nanoclusters acted as a catalytic site for the efficient oxidation reaction. The RBCT mechanism opens new opportunities for other efficient wide-bandgap semiconductors to be active under visible-light irradiation and is expected to be applicable for a wider range of applications.