Sub-stoichiometric tungsten oxide by the stearic acid method

Abstract

The synthesis of tungsten oxide by peroxotungstic route presents challenges, such as low solubility of tungstic acid in water and the fact that calcination product is a mixture of polytungstates. We propose a new route to obtain sub-stoichiometric tungsten oxides, using stearic acid, a non-toxic and low-cost material, as the dispersing and structuring agent for tungstic acid. The interaction between the precursor and the structuring agent was evaluated through chemical and structural analyses. Calcination of the stearic acid/tungstic acid systems produces vacant-rich monoclinic and orthorhombic tungsten oxides. Stearic acid plays a role of growth-directing agent and higher concentration of stearic acid promoted the growth of structures with plaque-shaped morphology in the samples, contributing to obtain sub-stoichiometric tungsten oxides, desired materials for visible light absorption.