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

Hatsukade, T., Stanford University
Kuhl, K. P., Stanford University
Cave, E. R., Stanford University
Abram, D. N., Stanford University
Jaramillo, T. F., Stanford University

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 (EB[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 EB[CO]; by exploring ways to increase the EB[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 EB[CO]. The silver surface was then nanostructured through an electrochemical oxidation/reduction process with the aim of strengthening the EB[CO]. This enhanced the production of CO2RR products compared to the unmodified surface. The enhanced activity is attributed to the possible shift in the EB[CO] of the surface as well as the increase in the surface area.