Enhanced Photoelectrochemical Activity of CuWO4 Photoanode by Yttrium Doping

Yttrium-doped copper tungstate photoelectrodes are prepared by depositing an yttrium-doped CuWO4 film (Y-CuWO4) on conductive glass substrates by dip coating. The morphology and chemical composition confirm the fabrication of yttrium-doped CuWO4 films. The optical bandgap of the photoelectrodes is studied by UV-vis diffuse reflectance and a bandgap of 2.30 eV is obtained for the pure CuWO4 photoelectrode. The yttrium-doped photoelectrodes show a small shift of the bandgap to higher values, which according to DFT calculations can be ascribed to a higher density of electronic states in the first conduction band from incorporating yttrium into the structure. The photoelectrochemical characterisation shows that adding yttrium produces an enhanced charge separation efficiency in the bulk which can be attributed to a higher donor density in the structure, and a 92.5% higher photocurrent density is obtained for the 5%Y-CuWO4 photoelectrode when compared to the pure CuWO4 photoelectrode for the oxygen evolution reaction at 1.3 V vs RHE. This work shows that doping CuWO4 with yttrium is an effective approach to improve the poor charge separation presented by pure CuWO4 photoelectrodes.