The insertion/de-insertion topotactic reactions in the Chevrel-type molybdenum cluster chalco-genides Mo6X8 (X = S, Se) are studied in the potentiodynamic mode on crystallite bed electrodes. We define the best conditions for the identification of the successive steps of the insertion (MxMo6X8). The phenomenon of the cation diffusion in the host lattice is responsible for the voltamperogram features.