A study of hydrated nanostructured tungsten trioxide as an electroactive material for pseudocapacitors

Agglomerates of tungsten trioxide in the range of 90 nm to 1 mu m are prepared by the acid precipitation method and characterized by XRD as well as scanning electron microscopy. The product when coated with platinum showed pseudocapacitance when in contact with acidic electrolyte in the potential range of 0.1 to -0.25 V/SCE. Capacitance in the range of 0.014 to 0.039 F cm(-2) exhibiting moderate potential dependencies measured through both chronopotentiometry and impedance spectroscopy is presumed to be due to the insertion/de-insertion of protons into the lattice of tungsten trioxide. Equivalent circuit consisting of parallel simulators of mass transfer and capacitor charging (insertion/de-insertion) fully compatible with the impedance measurements has been proposed and circuit parameters have been derived.