Structural, Optical, Band Edge and Enhanced Photoelectrochemical Water Splitting Properties of Tin-Doped WO3

The substitutional doping of tungsten oxide (WO3) with metal ions demonstrates a promising approach to enhance its photoelectrochemical (PEC) water splitting efficiency. In this article, the substitutional doping of Sn ions into WO3 lattice and its effect on optical, electrical, band edge, and PEC water splitting properties are explored. Sn-doped WO3 thin films were synthesized using a facile hydrothermal method. The characterization data reveal that the doping of Sn alters the morphology, induces multiple crystal phases, effects the crystal orientation, reduces the band gap, and increases the carrier density of WO3. With the uniform distribution of Sn ions in WO3 and the decreased charge transfer resistance at the electrode/electrolyte interface, the doped WO3 show notable enhancement in its PEC activity compared to the undoped WO3. The band edge study revealed that the introduction of Sn in WO3 lattice causes an increase in the energy distance between the valence band edge and Fermi level and, at the same time, induces a downward shift in both the valence and conduction band edges towards higher potentials with respect to reversible hydrogen electrode (RHE). Conclusively, this work shows significant and new insights about Sn-doped WO3 photoanodes and their influence on PEC water splitting efficiency.