ME Seminar - Towards the electrochemical reduction of CO2 in acidic media

Guest Speaker: Dr LUM Yanwei

Department of Chemical and Biomolecular Engineering
National University of Singapore

Dr LUM obtained his PhD degree in Materials Science and Engineering at the University of California, Berkeley in 2018 where he studied the electrochemical conversion of CO₂ into value-added chemicals and fuels. This was followed by a postdoctoral stint at the University of Toronto where he developed new electrochemical routes for ethylene upgrading. After this, he joined the Institute of Materials Research and Engineering, A*STAR as a scientist in 2019 and then the Department of Chemical and Biomolecular Engineering at the National University of Singapore as an Assistant Professor in 2021. His research interests include electrocatalytic CO₂ conversion and ammonia production/utilization.

Renewable electricity powered electrochemical CO₂ reduction (CO₂R) offers a valuable method to close the carbon cycle and reduce our overreliance on fossil fuels. However, high purity CO₂ is usually required as feedstock, which potentially decreases the feasibility and economic viability of the process. Direct conversion of flue gas is an attractive option but is challenging due to the low CO₂ concentration and the presence of O₂ impurities. As a result, up to 99% of the applied current can be lost towards the undesired oxygen reduction reaction (ORR). Here, we show that acidic electrolyte can significantly suppress ORR on Cu, enabling generation of multicarbon products from simulated flue gas. Using a composite Cu and carbon supported single-atom Ni tandem electrocatalyst, we achieved a multicarbon Faradaic efficiency of 46.5% at 200 mA cm-2, which is ~20 times higher than bare Cu under alkaline conditions. We also demonstrate stable performance for 24 h with a multicarbon product full-cell energy efficiency of 14.6%. Strikingly, this result is comparable to previously reported acidic CO₂R systems using pure CO₂. Finally, we show that a porous solid-state electrolyte can enable high current and selective CO₂R in a proton exchange membrane electrolyzer system. Our findings demonstrate a potential pathway towards designing efficient electrolyzers for direct conversion of flue gas to value-added chemicals and fuels.