Electrochemical hydrogen evolution reaction catalysed by a dinuclear cobalt complex with doubly N-confused hexaphyrin

In this study, we discovered the high catalytic activity of a dinuclear cobalt complex, Co2DNCH, supported by a doubly N-confused hexaphyrin (DNCH), a kind of ring-expanded porphyrin, for the electrochemical hydrogen evolution reaction. Co2DNCH catalysed electrochemical hydrogen evolution reaction with onset-overpotential eta = 0.45 V in water at pH 7.0, and with eta = 0.54 V and turnover frequency TOF = 2.27 x 10(4) s(-1) in DMF containing Et3NHCl as a proton source. Furthermore, electrochemical measurements and density functional theory calculations elucidated that the large pi-conjugated system of the DNCH ligand enables two-electron reduction centred on DNCH and hydrogen evolution at a relatively positive potential.