Influence of molybdenum doping on the structural, optical and electronic properties of WO for improved solar water splitting.

Doping WO with foreign atoms is a very efficient strategy to modify the structural, optical and electronic properties which could influence its photoelectrochemical (PEC) water splitting activity. In this study, we report a simple and efficient single-step strategy for the fabrication of molybdenum (Mo)-doped WO thin films. The characterization results show that doping Mo into WO leads to a significant change in the morphology without changing its crystal structure. Elemental mapping and EDS analysis revealed that Mo was homogeneously doped into the crystal lattice of WO in the at.% range of 0-10.31. The incorporation of Mo into WO reduced the band-gap of WO and increased its light absorption ability. Notably, X-ray photoelectron spectroscopic valence band-edge analysis confirmed that substitution of Mo into WO led to a downward shift in the conduction band minimum without any significant change in the valence band maximum with respect to Fermi level. The fabricated Mo-doped WO electrodes exhibited a higher photocurrent compared to undoped WO samples under simulated 1.5AM sunlight without the addition of a water oxidation catalyst. The procedure proposed herein provides a simple and systematic approach for the fabrication of band-gap-tailored WO photoanodes by Mo doping for efficient PEC water splitting.