Electrocatalytic H 2 evolution using binuclear cobalt complexes as catalysts.

We report herein on the use of two binuclear cobalt complexes with the N , N '-bis(salicylidene)-phenylmethanediamine ligand as catalysts for the H 2 evolution in DMF solution with acetic acid as proton source. Both experimental analyses (electrochemical analysis, spectroscopy analysis) and theoretical analysis (foot-of-the wave analysis) were employed. These catalysts required an overpotential of ca. 470 mV to catalyze the H 2 evolution and generated H 2 gas with a faradaic efficiency of 85-95% as calculated on the basis of after 5 hour bulk electrolysis. The kinetic investigation showed the maximal TOF value of 50 s -1 on the basis of an ECEC mechanism. Two cobalt centers, standing at a long distance of 4.175 Å, operated independently during catalysis without a synergetic effect or cooperation capability.