Rh-Doped SrTiO3 Photocatalyst Electrode Showing Cathodic Photocurrent for Water Splitting under Visible-Light Irradiation

A Rh-doped SrTiO3 (SrTiO3:Rh) photocatalyst electrode that was readily prepared by pasting SrTiO3: Rh powder onto a transparent indium tin oxide electrode gave a cathodic photocurrent under visible-light irradiation (lambda > 420 nm), indicating that the SrTiO3:Rh photocatalyst electrode possessed p-type semiconductor character. The cathodic photocurrent increased with an increase in the amount of doped Rh up to 7 atom %. The incident-photon-to-current efficiency at 420 nm was 0.18% under an applied potential of -0.7 V vs Ag/AgCl for the SrTiO3:Rh(7 atom %) photocatalyst electrode. The photocurrent was confirmed to be due to water splitting by analyzing the evolved H-2 and O-2. The water splitting proceeded with the application of an external bias smaller than 1.23 V versus a Pt counter electrode under visible-light irradiation and also using a solar simulator, suggesting that solar energy conversion should be possible with the present photoelectrochemical water splitting.