Cyclopentadienyl Cobalt Complexes as Precatalysts for Electrocatalytic Hydrogen Evolution

Abstract

Electrocatalytic hydrogen evolution is reported with a series of dicationic cobalt complexes [CpCo(N^N)(CH3CN)](ClO4)2 (Cp = cyclopentadienyl; N^N = bipyridine, pyrazolylpyridine, phenylazopyridine) using N,N‐dimethylformamidinium buffer as the proton source in acetonitrile. The catalytic current profiles obtained for each complex are very similar to each other with overpotentials ranging from 1.2 to 1.4 V, which suggests a common active catalytic species. Further electrochemical studies demonstrate that these complexes are unstable under electrocatalytic conditions: the bidentate nitrogen ligand is readily lost upon reduction in the presence of acid, initially generating [CpCo(CH3CN)3]+, which undergoes further decomposition to surface‐adsorbed species that are responsible for the observed electrocatalysis.