Electrochemical Behavior of Pyridinium and N-Methyl Pyridinium Cations in Aqueous Electrolytes for CO2 Reduction

The electrochemical reduction of aqueous pyridinium and N-methyl pyridinium ions is investigated in the absence and presence of CO2 and electrolysis reaction products on glassy carbon, Au, and Pt electrodes are studied. Unlike pyridinium, N-methyl pyridinium is not electroactive at the Pt electrode. The electrochemical reduction of the two pyridine derivatives was found to be irreversible on glassy carbon. These results confirmed the essential role of the N-H bond of the pyridinium cation. In contrast, the electrochemical response of N-methyl pyridinium ion at the glassy carbon electrode suggests that a specific interaction occurs between the glassy carbon surface and the aromatic ring of the pyridinium derivative. For all electrodes, an enhancement of current was observed in the presence of CO2. However, NMR spectroscopy of the solutions following electrolysis showed no formation of methanol or other possible byproducts of the reduction of CO2 in the presence of either pyridinium derivative ion.