The effects of W/Mo-co-doped BiVO4 photoanodes for improving photoelectrochemical water splitting performance

Abstract

The poor electrical conductivity of bismuth vanadate (BVO) can be improved by metal-doping at optimum percentage. Previously, we improved the photoelectrochemical (PEC) properties of BVO photoanodes by optimizing the different atomic percentage of molybdenum (Mo). Here, we co-doped BVO simultaneously with tungsten/molybdenum (W/Mo) to enhance the water splitting properties of BVO photoanodes. At optimum co-doping percentages of 0.5 %W-2%Mo BiVO4 (0.5W-2Mo-BVO) the photocurrent density maximum was ∼ 0.97 mA cm−2 at 0.6 V vs. Ag/AgCl. The water splitting was performed under 100 mW. cm-2 irradiation and 0.6 V vs. Ag/AgCl applied voltage for 0.5W-2Mo-BVO. The H2 production was 19.5 μmol.cm-2 after 2 h at optimized W/Mo co-doping. W/Mo co-doping into BiVO4 greatly improved the electron mobility, as demonstrated by photocurrent, Mott-Schottky, electrochemical impedance, open circuit potential (ΔOCP) and incident photon conversion efficiencies (IPCE) measurements. As compared to pure BVO, 0.5W-2Mo-BVO showed ∼2700-fold increase in the donor concentration (ND) and greatly decreased (1/60) space charge layer thickness (WSCL), which induced efficient charge carrier mobility and enhanced the PEC performance.