(414e) Effects of Surface Modifications On the Electrochemical Reduction of CO2 On Silver-Based Catalysts

Research on the electrochemical reduction of CO₂ has focused on gathering a fundamental understanding of the catalytic process through looking at a range of transition metals.  Carbon monoxide is believed to be a key intermediate and the CO binding energy (E_B[CO]) of the transition metal catalyst determines its activity for carbon dioxide reduction reaction (CO₂RR). We investigated CO₂ electroreduction on silver-catalyzed systems for two main reasons: (1) silver has high activity for CO₂RR to CO, and (2) it has a late onset for hydrogen evolution, an unwanted byproduct of electrochemical reduction in an aqueous environment. Silver is known to have a weak, sub-optimal E_B[CO]; by exploring ways to increase the E_B[CO] of silver, a higher activity of the CO₂RR may be attained, confirming the significance of the CO intermediate species.

Initial investigations using a polycrystalline silver surface were performed in a custom electrochemical cell, which offers high sensitivity for minor products of CO₂RR. As expected from literature, CO and H₂ were observed as major products, along with formate as a minor product. In addition to these products, methane, methanol, and ethanol were also detected as minor products at high overpotentials, illustrating the ability of silver to produce hydrocarbon/oxygenate products even with its weak E_B[CO]. The silver surface was then nanostructured through an electrochemical oxidation/reduction process with the aim of strengthening the E_B[CO]. This enhanced the production of CO₂RR products compared to the unmodified surface. The enhanced activity is attributed to the possible shift in the E_B[CO] of the surface as well as the increase in the surface area.