Kim, D. Choi, W. Lee, H.W. Lee, S.Y. Choi, Y. Lee, D.K. Kim, W. Na, J. Lee, U. Hwang, Y.J. Won, D.H. 2024-01-19T13:34:07Z 2024-01-19T13:34:07Z 2021-10-21 2021-10 2380-8195 https://pubs.kist.re.kr/handle/201004/116346 The direct conversion of low concentrations of CO2 is an essential approach, considering the expensive gas conditioning process for pure CO2, but has not yet been intensely studied in a membrane electrode assembly (MEA) electrolyzer. Herein, we explored the CO2 reduction with various CO2 concentrations in a zero-gap MEA electrolyzer and found that suppressing the hydrogen evolution reaction (HER) became more critical at low concentrations of CO2. We demonstrate that a Ni single-atom (Ni-N/C) catalyst exhibits a high tolerance toward low CO2 partial pressure (PCO2) because of the intrinsically large activation energy of the HER. Ni-N/C outperformed the CO productivity of Ag nanoparticles, especially at low concentrations of CO2 in the zero-gap MEA. When the PCO2 was lowered from 1.0 to 0.1 atm, Ni-N/C maintained >93% of CO Faradaic efficiency (FECO), but Ag nanoparticles showed a decrease in FECO from 94% to 40%. Furthermore, on the basis of a computational fluid dynamics simulation, we developed extrinsic operating conditions controlling the water transfer from the anolyte to the catalyst layer and improved CO selectivity at low CO2 concentrations in the MEA electrolyzer. ？ 2021 American Chemical Society. English American Chemical Society Electrocatalytic Reduction of Low Concentrations of CO2Gas in a Membrane Electrode Assembly Electrolyzer Article 10.1021/acsenergylett.1c01797 1 ACS Energy Letters, v.6, no.10, pp.3488 - 3495 ACS Energy Letters 6 10 3488 3495 N scie scopus 000707987500013 2-s2.0-85115658219 Chemistry, Physical Electrochemistry Energy & Fuels Nanoscience & Nanotechnology Materials Science, Multidisciplinary Chemistry Electrochemistry Energy & Fuels Science & Technology - Other Topics Materials Science Article Activation energy Binary alloys Catalyst selectivity Cobalt alloys Computational fluid dynamics Electrodes Electrolytic cells Ethanolamines Metal nanoparticles More electric aircraft Silver nanoparticles CO2 concentration CO2 reduction Conditioning process Direct conversion Electrocatalytic reduction Electrolyzers Gas conditioning Hydrogen evolution reactions Low concentrations Membrane electrode assemblies Carbon dioxide