Charge storage in WO3 polymorphs and their application as supercapacitor electrode material

Abstract

Tungsten oxide is a versatile material with different applications. It has many polymorphs with varying performance in energy storage application. We report simple and facile way to synthesize four phases of tungsten oxide from same precursor materials only by changing the pH and temperature values. Monoclinic, hexagonal, orthorhombic and tetragonal phase obtained, were analyzed and tested for supercapacitor application. The electrochemical analysis of four phases indicates that the hexagonal phase is best-suited electrode material for supercapacitor. The hexagonal phase exhibits higher specific capacitance (377.5 Fg−1 at 2 mV s−1), higher surface capacitive contribution (75%), better stability and rate capability of all four phases. Keywords: Supercapacitor, Tungsten oxide, Crystal phases, Surface controlled capacitance, Charge storage, Pseudocapacitive