The Potential Waveform In The Optical Switching Of Hydrated Nickel Oxide

In this work it has been analyzed the transient of the current flowing in an electrochemical cell in which the working electrode is constituted by a hydrated nickel oxide layer. The analysis of the current, utilizing a model for the diffusion mechanism of protons into the electrochromic material, allows to determine the diffusion coefficient for the oxidation and reduction processes. It ha5been observed that the diffusion coefficient for the bleaching process is larger than that one of the oxidation process. This fact could explain why the transition to the coloured phase occurs more rapidly than the inverse transition and with an apparently more simple function. Attempts have been made to put in correlation the eventual formation of metastable cristallographyc phases, observed by the X-rays diffraction technique, submitting the sample to a periodic potential, with a square waveform, for several cycles.