Electrochemical and chemical behavior of extra molybdenum atoms into the Chevrel phase host network

In this paper, we present a comparative electrochemical study of copper ins ertion into series of Mo6Se8-xSx phases which are obtained through differen t synthesis processes. We show that alpha-, beta-, and MT-forms can reversi bly accommodate copper at room temperature. The variation of the integral c opper insertion rate is a function of the sulfur content and the synthesis type of pseudobinaries, While the mechanism of copper intercalation is quit e similar for the different Mo6Se8-xSx for a given x, there is a drastic di fference for alpha- and beta-Mo6S8 compound. This behavior is explained on the basis of structural considerations. If the extra Mo atoms, present in t he lattice channels of the beta form and HT-Mo6Se8-xSx, are not displaced b y this copper intercalation, they are shown to be mobile through cationic e xchange reactions and chemical deinsertion at higher temperature. (C) 1999 Academic Press.