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 (N₂) 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