A new molecular electro-catalyst based on a triazenido–cobalt complex for generating hydrogen from both acetic acid and water

Abstract

The reaction of 1-[(2-carboxymethyl)benzene]-3-[2-pyridine]triazene (HL) with CoCl2·6H2O affords a six-coordinated cobalt(III) complex, [CoL3] 1, a new molecular electrocatalyst. Electrochemical studies show that complex 1 can catalyze hydrogen evolution from both acetic acid and water. Turnover frequency (TOF) reaches a maximum of 21 and 1973mol of hydrogen per hour at overpotential (OP) of 992mV (in DMF) and 838mV (in phosphate buffer, pH7.0), respectively. This performance is significantly better than those of other molecular cobalt catalysts reported in the literature for electrochemical hydrogen production. This is attributed to the ionic ligand, L− that coordinates strongly through four nitrogen atoms to the cobalt center, stabilizing the low oxidation state.