Photoelectrochemical properties of WO3 nanoparticulate thin films prepared by carboxylic acid-assisted electrodeposition

• Published in: Thin solid films 2013-10, Vol.544, p.191-196
• Main Authors: Kwong, W.L., Nakaruk, A., Koshy, P., Sorrell, C.C.
• Format: Article
• Language: English
• Subjects: Carboxylic acids; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electrodeposition; Electrodeposition, electroplating; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport phenomena in thin films and low-dimensional structures; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Photoconduction and photovoltaic effects; photodielectric effects; Photocurrent; Physics; PTA; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; WO3 thin films
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2013.03.125

Optimisation of particle sizes of WO3 films is important for photoelectrochemical applications. However, most of the developed size-controlled synthesis techniques involve complicated instruments or vacuum systems. The present work presents an alternative method using carboxylic acid-assisted electrodeposition where WO3 thin films were deposited from peroxotungstic acid (PTA) solution containing different carboxylic acids (formic, oxalic, citric). The effects of carboxylic acids on the electrodeposition and the resultant morphological, mineralogical, optical, and photoelectrochemical properties of the WO3 films were investigated. The analysis showed that the films consisted of equiaxed nanoparticulate monoclinic WO3. The deposition thicknesses and the average grain (individual particle and agglomerate) sizes of the films were dependent on the amount of hydronium ions and the molecular weight and associated sizes of the conjugate bases released upon the dissociation of carboxylic acids in the PTA solutions, which result in hydrogen bond formation and molecular dispersion. The photocurrent densities of the films deposited with carboxylic acids were greater than that of the film deposited from pure PTA. These differences were attributed to improvements in (1) grain size, which controls photogenerated electron-hole transport, and (2) effective grain boundary area, which controls the numbers of active reaction sites and electron-hole recombination sites. •Carboxylic acid-assisted electrodeposition of WO3 films from peroxotungstic acid.•The types of carboxylic acids control the deposition rates and microstructure.•WO3 grain sizes and effective grain boundary areas determine the photocurrents.•Maximal photocurrent measured in the smallest-aggregate films (~83nm).