H2 oxidation by cobaloximes: Mechanistic insight into hydrogen evolution catalysis

Abstract

Cobaloximes are a series of macrocyclic cobalt complexes that have been shown to catalyze the hydrogen evolution reaction (HER) at low overpotentials. There has been much debate about the mechanism of this reaction, particularly with regard to H-H bond formation. As catalysts that operate close to the thermodn. potential, cobaloximes show some degree of reversibility, oxidizing hydrogen in the presence of base to form the conjugate acid. Presented here are kinetic studies of the cobaloxime-mediated oxidn. of hydrogen in the presence of base. Insight into the bifurcation between homolytic and heterolytic mechanisms of cobaloximecatalyzed HER is gained by studying the microscopic reverse reaction.

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