The Electrochromic Process at Nb2 O 5 Electrodes Prepared by Thermal Oxidation of Niobium

Electrochromism was studied with layers prepared by thermal oxidation of niobium. The layers are crystalline and the morphology and thickness of these films play an important role in the response of electrochromic process. Cyclic voltammetry and chronopotentiometry were carried out together with ellipsometric measurements in electrochromic region. ESCA spectra of the electroreduced oxide suggest that Nb(V) is reduced to a lower valence state such as Nb(IV), and a chemical bond is formed between H + inserted into the oxide and O −2 of the oxide. For films the coloration is due to a simultaneous injection of electrons and H + ions.