Nanotextured pillars of electrosprayed bismuth vanadate for efficient photoelectrochemical water splitting

We demonstrate, for the first time, electrostatically sprayed bismuth vanadate (BiVO₄) thin films for photoelectrochemical water splitting. Characterization of these films by X-ray diffraction, Raman scattering, and high-resolution scanning electron microscopy analyses revealed the formation of nanotextured pillar-like structures of highly photoactive monoclinic scheelite BiVO₄. Electrosprayed BiVO₄ nanostructured films yielded a photocurrent density of 1.30 and 1.95 mA/cm² for water and sulfite oxidation, respectively, under 100 mW/cm² illumination. The optimal film thickness was 3 μm, with an optimal postannealing temperature of 550 C. The enhanced photocurrent is facilitated by formation of pillar-like structures in the deposit. We show through modeling that these structures result from the electrically-driven motion of submicron particles in the direction parallel to the substrate, as they approach the substrate, along with Brownian diffusion. At the same time, opposing thermophoretic forces slow their approach to the surface. The model of these processes proposed here is in good agreement with the experimental observations.