Nanotextured Pillars of Electrosprayed Bismuth Vanadate\nfor Efficient Photoelectrochemical Water Splitting

Abstract

We\ndemonstrate, for the first time, electrostatically sprayed bismuth\nvanadate (BiVO₄) thin films for photoelectrochemical water\nsplitting. Characterization of these films by X-ray diffraction, Raman\nscattering, and high-resolution scanning electron microscopy analyses\nrevealed the formation of nanotextured pillar-like structures of highly\nphotoactive monoclinic scheelite BiVO₄. Electrosprayed\nBiVO₄ nanostructured films yielded a photocurrent density\nof 1.30 and 1.95 mA/cm² for water and sulfite oxidation,\nrespectively, under 100 mW/cm² illumination. The optimal\nfilm thickness was 3 μm, with an optimal postannealing temperature\nof 550 °C. The enhanced photocurrent is facilitated by formation\nof pillar-like structures in the deposit. We show through modeling\nthat these structures result from the electrically-driven motion of\nsubmicron particles in the direction parallel to the substrate, as\nthey approach the substrate, along with Brownian diffusion. At the\nsame time, opposing thermophoretic forces slow their approach to the\nsurface. The model of these processes proposed here is in good agreement\nwith the experimental observations.