Electrochemical Properties of  WO 3 · x (  H 2 O  ) : II . The Influence of Crystallization as Hydration

Abstract

Electrochemical properties of WO3 films prepared by vacuum evaporation and stored in high humidity atmosphere have been studied in organic electrolytes. Structures of the film have been analyzed by electron diffraction analysis and x‐rays. It has been found that the evaporated amorphous WO3 film is crystallized to form WO3·H2O crystal and furthermore H2WO4·H2O from surface layer to bulk layer in high humidity air. Hydrated WO3·xfalse(H2Ofalse) crystal layer may act as a high resistant layer on the electrochemical reaction, so that the hydrated layer, remarkably, loses the electrochromic activity.

Microstructural and electrochromic properties of tungsten oxide thin films produced by surfactant mediated electrodeposition

“…6(a)) and 1620 cm À1 (Fig. 6(b)) arise due to the H-O-H deformation [25]. The band at 824 cm À1 observed in the spectra of the films before and after immersion is attributed to the n(W-O) stretching mode of hexagonal WO 3 .…”

Amorphous WO3 Films via “Wet” CVD of a WVI Oxoalkoxide Precursor

“…This phenomenon is explained by the presence in the matrix of a high hydrogen content, known to accelerate the electrochemical processes in this type of material. [17,18] On the other hand, the presence of OH groups was previously shown by physical± chemical characterization of the material (X-ray photoelectron spectroscopy (XPS) analysis). Coloration±decoloration processes are fast, even after repeated cycles (not shown), but the electrochromic properties of the films appear to be progressively damaged (e.g., appearance of a residual coloration after every cycle).…”

Catalytic activity of platinum/tungsten oxide nanorod electrodes towards electro-oxidation of methanol

“…According to Yoshiike and Kondo [19,20], water molecules are not only physisorbed but also chemisorbed on WO 3 . The oxophilic nature of WO 3 would help in adsorbing the intermediates and thereby, maintain the surface of platinum clean.…”