Fabrication of CdS photoelectrodes coated with titania nanosheets for water splitting with visible light

We attempted to fabricate visible-light responsive photoelectrodes with catalytic activity of water oxidation by coating CdS electrodes with titania nano sheets. Titania coated CdS electrodes were prepared by ionic adsorption with two kinds of cationic polymers and eight kinds of metal ions. The coating with polydiallyldimethyl ammonium cations and polyethyleneimine could not suppress the photo corrosion in Na2SO4 solution. The CdS/titania electrodes prepared with Cu(II), Ni(II), and In(III) ions showed no photocurrent at the applied potential of 0.20 V (vs. Ag/AgCl) though the dissolution was suppressed. The electrodes prepared with Fe(II), Mn(II), and Co(II) showed corrosion in the dark on the slightly anodic polarization, similarly to that observed for a bare CdS electrode. On the other hand, the electrodes prepared with Zn(II) and Cd(II) demonstrated no corrosion on the same condition, but under visible light irradiation the CdS corroded. These observations indicate that the surface of titania nanosheet does not have the catalytic active site for water oxidation, or there is a barrier to transfer holes across the nanosheet.