"Electrochemically modulated intercalation and reduction processes of nanostructured WO₃ films",

M. Hepel, H. Redmond,

Department of Chemistry, State University of New York at Potsdam, Potsdam, NY

Electrochromic properties and optical density modulation in WO₃ films have been studied to elucidate the mechanism of reversible ion intercalation and formation of color centers. The intercalation and electrostatic attachment of inorganic cations and alkyl ammonium cations to WO₃ nanoparticles have been investigated using Electrochemical Quartz Crystal Nanobalance (EQCN) and spectroscopic techniques. Strong dependence of the cation ingress on the degree of cation hydration in aqueous solutions has been found. The competition of metal cation intercalation with the uptake of hydronium ions by WO₃ films has been observed. The limited mass increases for some cations have been attributed to local water dissociation and hydronium ion uptake. These processes result in pH increase and WO₃ reduction, the strongest effect being observed in the presence of alkyl ammonium cations. Improvements in the electrooptic switching performance of WO₃ films have been achieved by shortening the solid-state diffusion paths and nanostructured film design.