ELECTROCATALYTIC PROPERTIES OF MIXED TRANSITION-METAL TELLURIDES (CHEVREL-PHASES) FOR OXYGEN REDUCTION

Pseudobinary molybdenum cluster tellurides (Chevrel phases) with mixed transition metal clusters of the type M(x)Mo(6-x)Te(8) (M = Pt, Os, R u, Rh) and the binary phase Mo6Te8 have been synthesized, structurally characterized and electrochemically investigated with respect to thei r electrocatalytic properties for oxygen reduction. A correlation of t he number of electrons per cluster unit (NEC) with the open circuit po tential (o.c.p.) in saturated oxygen electrolyte was found. The limita tion of the o.c.p. values are due to the mixed potential developed wit h each electrode material due to molybdenum oxidation. The lowest corr osion tendency and highest catalytic activity are found in the telluri de phases when NEC (in the valence band) approaches 24.