Cathodic insertion of ions in tungsten(VI) oxide from aqueous media

摘要

Electrochemical insertion of ions in monoclinic tungsten(VI) oxide from aqueous was investigated at room temperature. The solutions were nitric acid and solutions of Group I and II nitrates. In all the performed insertions, except with lithium nitrate, the obtained intercalates had the composition H_xWO_3 (0.07 < x < 0.84). Within this compositional range two types of hydrogen intercalated materials were obatined, both with tetragonal symmetry. For low degrees of insertion (0.07 < x < 0.17) the lattice constatns were a = b = 5.225(2) and c = 3.884(4) A. For high degrees of insertion (0.50 < x < 0.84) the lattice constants were a = b = 5.358(2) and c = 3.749(5) A. With lithium ntrate as electrolyte solution intercalates with composition Li_xWO_3 were obtained. After exposure to air the lithium intercalated compounds were tetragonal with lattice constants a = b = 5.1996(2) and c = 3.8402(1) A. The processes where barium nitrate was used electrolyte were studied in detail, and the electorchemical processes were determined. The intercalates were characterized using X-ray powder diffraction, and Rietveld refinements of the structures of H_(0.12)WO_3 and Li_xWO_3 were performed.