The electrochromic behavior of phosphotungstic acid (PWA), a heteropoly compound was investigated. The electrochemical and in-situ spectroelectrochemical measurements showed that by electrochemical oxidation and reduction, phosphotungstic acid can be bleached and colored, respectively. The colorttion efficiency of PWA in an aqueous solution was found to be 16.8 cm²/C. This is lower than that observed with WO₃ films presumably due to continuous dissolution of the reduced species. The diffusion coefficient of phophotungstate anions [PW₁₂O₄₀^-3] was found to be 2.8 x 10^-5 cm²/s. The fraction of the number of protons per WO₃ molecule involved in the electrochemical reaction was determined ty the EMF measurments, and was found to be >0.2.

Date Published: 12 December 1989
PDF: 8 pages
Proc. SPIE 1149, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion VIII, (12 December 1989); doi: 10.1117/12.962163

Published in SPIE Proceedings Vol. 1149:
Optical Materials Technology for Energy Efficiency and Solar Energy Conversion VIII
Claes-Goeran Granqvist; Carl M. Lampert, Editor(s)