2024 AIChE Annual Meeting
(569eh) Influence of Different CO2 Sorbents on the Direct Electrochemical Captured CO2 Reduction Using Silver Catalyst
Authors
Kowalski, R. M., University of California, Los Angeles
Yue, C., University of California, Los Angeles
Gracia, S., University of California, Los Angeles
Cheng, D., University of California, Los Angeles
Sautet, P., University of California, Los Angeles
Morales-Guio, C., University of California, Los Angeles
In the context of carbon reutilization, the direct electroreduction of captured CO2 (c-CO2RR) appears as an appealing approach since it would avoid the energetically costly separation of CO2 from the capture agent. In this process, the CO2-bound adduct is directly reduced from its captured form, producing a fuel or chemical and regenerating the capture agent in the same process step. Here we investigate the influence of capture agent and proton source. Specifically, we consider methoxide captured CO2, NH3 captured CO2, and bicarbonate on silver electrocatalysts. The CO2 capture media is a complex space of several buffer reactions that allow the co-existence of different carbon species in solution depending on CO2 loading, temperature, pressure, and pH. Through a rotating cylinder electrode cell of well-defined mass transport properties, we identify the active carbon species undergoing reduction. It is concluded that the CO generated is via CO2RR from small amounts of dissolved CO2 present in the solution. We further observe that the c-CO2RR cannot compete with HER on Ag and the dominant product observed is H2 with low amounts of CO being produced. Although methanol solvent exhibits a lower HER activity, HER remains dominant over c-CO2RR, highlighting the importance of mitigating HER to enhance the viability of c-CO2RR. This talk will also discuss the role of porosity of the electrode as well as temperature in the rate of generation of CO2 reduction products and will determine optimum conditions of operation for the improved production of CO from captured CO2. Our work further suggests that methoxide is a potential alternative capture agent to NH3 for direct reduction of captured CO2, though challenges in catalyst design—particularly in reducing the onset potential of c-CO2RR to surpass HER—remain to be addressed.