Electrocatalytic reduction of CO 2 with CCC-NHC pincer nickel complexes.

A CCC-NHC pincer Ni(II) Cl complex was prepared according to the metallation/transmetallation methodology. It was fully characterized by electrochemical, NMR spectroscopic, theoretical, and X-ray crystallographic methods. The complex and its cation were evaluated for electrocatalytic reduction of CO2 under a variety of conditions and found to provide some of the fastest catalytic rates and highest substrate selectivities (CO2 vs. H+) reported. Rates improved in the presence of water and, significantly, catalysis occurred at the first reduction potential, presumably at the Ni(I) state. Controlled potential electrolysis (CPE) was found to yield CO at 34% and formate at 47% Faradaic efficiency (FE).