Electrochemical reduction of carbon dioxide with a molecular polypyridyl nickel complex

Abstract

The synthesis and reactivity of a molecular nickel(II) complex 1 with the polypyridyl ligand framework N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) under electrochemically reducing conditions in the presence of CO₂ is reported. Cyclic voltammetry (CV), infrared spectroelectrochemistry (IR-SEC) and electrolysis experiments suggest this Ni complex is competent at mediating the two-electron reduction of CO₂ to CO and H₂O with phenol as an added proton donor, but is subsequently prone to rapid degradation as Ni(CO)₄. This deleterious pathway was shown to be mitigated by the inclusion of the CO scavenger [Ni(TMC)]²⁺, although this requires stoichiometric inclusion for each catalyst turnover and does not significantly improve the observed catalytic current densities.