Aqueous electrochemical insertion of Na + into the tungsten oxide hybrid WO 3(4,4′-bipyridyl) 0.5

Abstract

Aqueous electrochemical insertion of M + (Na + and H +) species into WO 3(4,4′-bipyridyl) 0.5 has been carried out. The chemical states and structure of the resulting product were analysed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). XPS showed the presence of W 6+ as well as the usual reduced W species (W 5+) which is responsible for a change in colour. Moreover, the presence of these intercalates correlates with the evolution of the reduced W species. The bulk structure of the layered hybrid, as determined by powder X-ray diffraction, showed no alteration after electrochemistry, in contrast to the same measurements on tungsten trioxide (WO 3). This however concurs with single-crystal X-ray studies, which show little change in lattice parameters with Na + insertion. Four-probe resistance measurements of the layered hybrid coated film display a drop in resistance after electrochemistry, which can be attributed to the injection of charge-carriers into the conduction band.