Direct growth of duel-faceted BiVO4 microcrystals on FTO-coated glass for photoelectrochemical water oxidation

Abstract

In this study, we report on the direct growth of duel-faceted BiVO4 microcrystals on fluorine-doped tin oxide (FTO) coated glass by simple chemical bath deposition as photoanode material for PEC water oxidation. Crystal growth and particle density were affected by bath temperature; films grown in higher bath temperature (95 °C) showed great surface coverage and larger particle sizes, as indicated by scanning electron microscopy (SEM) images. X-ray diffraction (XRD) studies revealed that BiVO4 predominantly occurs in the form of monoclinic scheelite crystal structure in all deposited films. UV–vis spectroscopy and X-ray photoelectron spectroscopy (XPS) investigations confirmed the existence of pure BiVO4. High-temperature treatment of the film was found to improve crystallinity and preferential growth of dual-faceted ((010), (110)) BiVO4 microcrystals. An optimized electrode exhibited excellent PEC water oxidation performance, with 0.78 mA.cm−2 of photocurrent density at 1.23 V versus a reversible hydrogen electrode (RHE) under standard illumination (100 mW.cm−2 and AM 1.5), which was increased up to 1.23 mA.cm−2 before dark current started to flow. The electrode also showed good stability when exposed to longer illumination in a 0.5 M Na2SO4 solution, and n-type character. These findings are thus important for the development of a simple method for synthesis of BiVO4 microcrystals as efficient electrode material for PEC water splitting.