Excellent electrocatalytic activity of benzil for direct reduction of CO2 as well as indirect reduction of pyridine: A kinetic view of the electrocarboxylation process

Abstract

Benzil, 1,2-diphenylethane-1,2-dione, was used as an excellent electrocatalyst for reduction of carbon dioxide, CO2. The reduction overpotential of CO2 was reduced about 900mV in the presence of a benzil mediator. The chemical reaction of the product of the electrocatalytic reduction of CO2, (activated CO2, CO2•−) with pyridine at a glassy carbon electrode, GCE, surface and in an acetonitrile-But4NClO4 solution was investigated by cyclic voltammetry, chronoamperometry and controlled potential coulometry. By chronoamperometry, the catalytic rate constant, k, for the electron transfer between benzil and CO2 was obtained as 8.1±0.4M−1s−1. The results indicate that pyridine has a strong interaction with the activated CO2. The coulometry method was used to obtain the product of the pyridine chemical reaction with CO2•−. The spectral characterizations of FTIR, 1H and 13C NMR of the coulometry experiment product proved that the pyridine anion radical, Py•−, was carboxylated by CO2•−, and isonicotinic acid is the final major product.