Pyridine and Pyridinium Electrochemistry on Polycrystalline Gold Electrodes and Implications for CO2 Reduction

We examine the electrochemical behavior of pyridine (py) and pyridinium ion (pyrH(+)) on gold electrodes in inert nitrogen (N-2) and carbon dioxide (CO2) environments to evaluate potential catalytic roles of nitrogen heterocycles in electrochemical CO2 reduction. Analysis of the pyridine and pyridinium systems shows that gold electrodes exhibit unique pyrH(+) and CO2 electrochemistry compared with previous work on platinum electrodes or photoelectrode systems. Specifically, analysis of the data shows specific adsorption of pyridine/pyridinium, an irreversible reduction wave at -1.0 V vs Ag/AgCl associated with the one-electron reduction of pyridinium, and an enhanced reductive current when CO2 and pyrH(+) are included together in the aqueous solution. Our results show no evidence to support formation of carbon-containing reduction products and implicate CO2 as a possible weak acid catalyst for production of dihydrogen.