Nickel-doped and surface fluorinated tungsten trioxide photoanode with enhanced photoelectrochemical water oxidation

To improve the slow charge transfer and high electron-hole recombination rate of tungsten trioxide (WO3), a nickel-doped and surface fluorinated WO3 photoanode is proposed. Compared with the unmodified and one-step modified WO3 photoanodes, the co-modified F/Ni-WO3 with two steps exhibits superior photoelectrochemical (PEC) performance with a significantly high photocurrent density of 1.03 mA/cm2 compared to 0.51 mA/cm2 of bare WO3 at 1.23 V vs. RHE. Ni doping can accelerate the kinetics of water oxidation and extend the light absorption range of the WO3 photoanode, while surface fluorination can enhance the surface electronegativity and hydrophilicity of the WO3 photoanode. The synergistic influence of the Ni doping and surface fluorination results in a lower carrier transport impedance, higher charge separation efficiency and larger electrochemically active surface of the WO3 photoanode which eventually contribute to the enhanced PEC performance for water oxidation.