Large-scale synthesis of functional tungsten oxide with controlled oxygen-deficiency by a continuous screw reactor

Abstract

Oxygen-deficient tungsten oxide is one of the promising materials for broad applications due to its enhanced characteristics owing to the oxygen-deficiency. Development of a mass production process is crucial in consideration of the increasing demand of this material in industrial purposes. A continuous screw reactor was employed to the production of oxygen-deficient tungsten oxide. The effects of hydrogen concentration and the reduction time on the composition of products were investigated. The maximum WO2.72 mole fraction of 0.95 was achieved by optimum hydrogen concentration and reduction time. X-ray Photoelectron Spectroscopy (XPS) spectra of the products indicated the introduction of oxygen-deficiency. Anisotropic crystal growth in the (010) direction is found in the cross-section observation by Scanning Electron Microscope (SEM). The displacing value from High-Resolution Transmission Electron Microscope (HR-TEM) demonstrated the existence of WO2.72. The reaction kinetic was investigated by thermogravimetric analysis. Estimated activation energy supported the results from the continuous process. This work suggests the promising process for the large-scale production of functional materials.