Electrostatic spray deposition of transparent tungsten oxide thin-film photoanodes for solar water splitting

• Stable WO3 thin-film photoelectrodes for water splitting applications were prepared with the electrostatic spray deposition.
• The thickness of the films prepared was varied from 50 to 400 nm.
• The photocurrent of the WO3 thin films reached the maximum value of 0.40 mA/cm2.

Photocatalytic water splitting has been explored extensively as a promising way to capture and store solar energy. In this study, stable WO3 thin-film photoelectrodes for water splitting applications were prepared with the simple, inexpensive, and scalable technique of electrostatic spray deposition. The physicochemical, structural, optical, and morphological properties of the WO3 films were studied with X-ray diffraction, Raman spectroscopy, UV–visible spectroscopy, and scanning electron microscopy. The thickness of the films prepared was varied from 50 to 400 nm in order to establish a relationship between film thickness and water splitting performance. The photocurrent of the WO3 thin films, measured in a 0.5 M Na2SO4 electrolyte solution against a standard Ag/AgCl reference electrode, increased with increasing film thickness. The film electrosprayed for 10 min exhibited a photocurrent density of 0.04 mA/cm2. The photocurrent density was increased by 10-fold to 0.40 mA/cm2 when the electrospraying time was increased to 60 min. Of all the films tested in this study, the film electrosprayed for 60 min, which had a thickness of 400 nm, showed the best photoelectrochemical cell activity.

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