Electrodeposited WO3 Film on Various Metal Substrates and Its Morphological Effect for Photoelectrochemical Water Splitting

Abstract

Metal oxides such as TiO2, WO3, ZnO, SnO2 etc. have widely investigated because of low cost, environmental friendliness, and the application to various energy related devices. In particular, WO3 having the energetic band gap of about 2.8 eV has the absorption of more visible light, the suitable position of conduction band to transfer the photogenerated electrons to the substrate, and the stable photoresponse in the strong acidic condition. Herein, we prepared the WO3 film by electrodeposition that provides the clean and reproducible technique. That is, a compact structured WO3 film with a thickness of 780 nm was prepared by facile electrodeposition at a constant potential of -0.47 V versus saturated Ag/AgCl electrode. For a nanoporous structured WO3 film, polystyrene (PS) beads with a size of 320 nm were used as the template, and the electrodeposition was performed under the same experimental conditions by varying the reaction time from 1 to 3 min to adjust the thickness of the depositing layer. The PS beads were completely removed from the template by the calcination at 450 °C for 3 h under air, affording inverse opal WO3 films with a pore size of 300 nm. For the inverse opal WO3 film with a thickness of 790 nm prepared by electrodeposition for 1 min, the highest photocurrent density (1.75 mA/cm2 at 1.5 V versus sat. Ag/AgCl) was achieved, followed by compact WO3, inverse opal WO3 (2 min), and inverse opal WO3 (3 min) films with photocurrent densities of 1.2, 0.74, and 0.35 mA/cm2, respectively. The further discussion on the morphological and crystalline properties of the prepared WO3 film was confirmed by a field emission scanning electron microscope and X-ray diffraction.