Insight into the electrochemical reduction of CO₂ on gold via surface-enhanced Raman spectroscopy and N-containing additives

Due to increasing levels of greenhouse gases in the atmosphere, increased attention has been given to minimizing their emissions and reducing current levels. Primarily focusing on CO₂, routes towards reducing atmospheric levels include capture, sequestration, and conversion. For CO₂ conversion, Au electrocatalysts have demonstrated high CO₂ reduction activity to CO which can then be further converted to various synfuels or commodity chemicals. In this work, we further probe Au electrocatalysts by utilizing a Ag-based model, using N-containing additives, such as pyrazole and benzotriazole, and surface-enhanced Raman spectroscopy. Surface-enhanced Raman spectroscopy (SERS) reveals that only in the presence of N-containing additives is a stronger CO band seen. These additives do not affect the CO₂ reduction mechanism of Au, as found by Tafel and product distribution analysis. We also demonstrate enhancement of the CO₂ reduction rate on Au by utilizing a known CO₂ scavenger, ethanolamine, adsorbed on the Au surface. This result suggests that improving CO₂ reduction should focus on the reactant side of the Sabatier plot.