Synthesis and characterization of osmium carbonyl cluster compounds with molecular oxygen electroreduction capacity

A transition metal cluster electrocatalyst based on Osx(CO)n was synthesized by pyrolysis of Os3(CO)12 in 1,2-Dichlorobenzene (b.p.≈180°C) under inert atmosphere (N2). The electrocatalytic parameters of the oxygen reduction reaction (ORR) for an Osx(CO)n catalyst were studied with a rotating disk electrode in 0.5 M H2SO4 electrolyte. The diffusion coefficient and solubility of O2 in 0.5 M H2SO4 were calculated. Koutecky–Levich analysis of the linear voltamperometry data showed that the reaction follows first-order kinetics and the value of the Koutecky–Levich slope indicates a multielectron charge transfer during the ORR. The value of the Tafel slope obtained from the mass transfer corrected Tafel plots is 131 mV/decade. The performance of the catalyst in a H2/O2 PEM fuel cell cathode was evaluated and found to be nearly as good as that of Pt.