ELECTROCHROMIC REACTIONS IN MANGANESE OXIDES .1. RAMAN ANALYSIS

The reactions taking place during voltametric cycling of manganese oxi des can be determined using in situ Raman spectroscopy. The main diffi culty for the oxide identification is to obtain relevant Raman referen ce spectra because of the many possible compounds and, for some of the se compounds, of their instability in the laser beam. As a consequence , several modifications of different tetra-, tri- and divalent mangane se oxides and oxyhydroxides were carefully studied. The electrochromic behavior of three types of manganese oxides, two prepared by thermal oxidations and the other by electrochemical deposition, were then comp ared. The presence of nonstoichiometry in the pristine material was ne cessary to obtain a reversible electrochromic effect. The reaction dur ing electrochromic cycling is more complicated than a simple passage f rom MnO2 to MnOOH.