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7756807 
Journal Article 
Color impedance and electrochemical impedance studies of WO3 thin films: H+ and Li+ transport 
Kim, JJ; Tryk, DA; Amemiya, T; Hashimoto, K; Fujishima, A 
1997 
1 
Journal of Electroanalytical Chemistry
ISSN: 1572-6657
EISSN: 1873-2569 
Elsevier 
435 
1-2 
31-38 
English 
WOS:A1997YL18500005 
Ac potential-modulated optical transmittance (color impedance) and electrochemical impedance measurements were employed in an in situ investigation of the electrochromic behavior of evaporated amorphous tungsten trioxide (a-WO3) films in non-aqueous (LiClO4 + propylene carbonate), aqueous acid (H2SO4) and mixed non-aqueous-aqueous acid (PC + HClO4) electrolytes. The optical and electrochemical responses were essentially the same with the 0.8 μm thick films that were examined, indicating that all of the injected charge was involved in the faradaic process. The behavior of the WO3 films in LiClO4 + PC and H2SO4 electrolytes was relatively simple compared to that of the PC + HClO4 electrolyte, in which the charge transfer resistances and diffusion coefficients were found to vary considerably with potential, probably due to a shift from proton insertion at more positive potentials to lithium ion insertion at more negative potentials. In all of the electrolytes, evidence was seen for two types of diffusion processes, a slower one, most likely due to diffusion within small clusters of WO6 octahedra, and a faster one, due to diffusion in nanometer-scale spaces between these clusters. © 1997 Elsevier Science S.A. 
H+ and Li+ transport; electrolytes; tungsten trioxide