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 insertion into series of Mo6Se8−xSx phases which are obtained through different synthesis processes. We show that α-, β-, and HT-forms can reversibly accommodate copper at room temperature. The variation of the integral copper insertion rate is a function of the sulfur content and the synthesis type of pseudobinaries. While the mechanism of copper intercalation is quite similar for the different Mo6Se8−xSx for a given x, there is a drastic difference for α- and β-Mo6S8 compound. This behavior is explained on the basis of structural considerations. If the extra Mo atoms, present in the lattice channels of the β form and HT-Mo6Se8−xSx, are not displaced by this copper intercalation, they are shown to be mobile through cationic exchange reactions and chemical deinsertion at higher temperature.