Spectroelectrochemical Study of the Role of Pyridinium in Carbon Dioxide Reduction

Pyridinium (pyrH⁺) has been studied for its potential catalytic role in the electrochemical reduction of carbon dioxide (CO₂) to methanol. We report electrochemical analysis of the pyrH⁺ + CO₂ interaction on metallic electrodes, independently of the hydrogen evolution reaction. Present results show that gold electrodes exhibit unique pyrH⁺ and CO₂ electrochemistry compared with previous work on platinum electrodes or photochemical systems. Analysis of the electrochemical data show multi-layer adsorption of pyridine, an irreversible reduction wave associated with pyrH⁺ as the pH approaches the pK_a of pyrH⁺, and a small but significant catalytic activity (0.15 mA/cm²) for CO₂ reduction in the presence of pyrH⁺ at -1.0 V vs. Ag/AgCl.

The present work aims to discern the electroreduction mechanism by analyzing the proposed pyrH⁺ reduction process in inert purge gas environments using electrochemical and in situ infrared and Raman spectroscopic techniques. This information will guide the analogous exploration under CO₂ environments to determine the nature of the enhanced current response. Possible products from the pyrH⁺ + CO₂ electroreduction will be discussed.