(17b) Mechanistic Studies of the Electrochemical Reduction of CO2 on Gold

The lack of mechanistic understanding of electrode mediated CO₂ electrochemical reduction is a severe barrier in development of active and selective electrocatalysts for CO₂ reduction. Au is an ideal material for initial mechanistic studies due to its high selectivity toward a single product (CO). Vibrational spectroscopy, electrokinetic studies, isotopic labeling, and mass spectroscopy were combined in the mechanistic study of CO₂ reduction on Au electrodes. We demonstrate for the first time that pH near the electrode surface is significantly elevated relative to the bulk. In addition, we propose that adsorption of metal cations at sufficiently low potentials could be a key factor in limiting the transport of reactants to the electrode surface, thus suppressing the reaction rate.