(10g) Modeling Aqueous Hydroxide Ions As a Guide for CO2 Electrocatalytic Reduction

The conversion of CO₂ into fuels and oxygenates can be performed thermochemically and electrochemically, particularly on copper (Cu) catalysts. A known observation is the contrasting product distributions obtained when one undergoes CO₂ hydrogenation as compared to the product distribution in CO₂ electroreduction; for example, methanol is a major hydrogenation product rarely observed in electroreduction. Although the mechanistic model for CO₂ hydrogenation has largely reached consensus, the mechanistic pathways for CO₂ electroreduction remain open to discussion. Proposed mechanisms in CO₂ electroreduction are tied closely with our ability of modeling electrochemical energetics in aqueous solution. Herein, we use a recently developed electrode model to describe an alternative pathway from CO₂ to CO on silver (Ag(100)) and CO₂ to methane and ethylene on Cu(100), and show the difference between the model and the CHE model and grand canonical models. Microkinetics remains in agreement with experimental observations of Tafel slopes in both cases. This work reinterprets the role that charged ions have on shaping mechanistic pathways in aqueous solutions, putting spotlight on anions venturing near the cathode as non-spectating species in electrocatalytic reactions.