(682b) Electrochemical Conversion of Low Concentration CO2 Gas in a Membrane Electrode Assembly Electrolyzer

Electrochemical CO₂ reduction to valuable chemicals is a promising technology for mitigating the global climate crisis and developing new processes for chemical production. The recent development of an electrolyzer gave a remarkable advancement of CO₂ reduction performance in production rate and selectivity. In particular, a membrane electrode assembly (MEA) electrolyzer whose electrodes and membrane are assembled without a catholyte has been studied as a promising configuration for stackable applications. To increase the practical applicability of the CO2 reduction system, the direct conversion of low concentrations of CO₂ is an essential approach due to the expensive gas conditioning process for pure CO₂, which is required for reactant for electrochemical CO₂ reduction. In this research, we explored the CO₂ reduction with various CO₂ concentrations in the MEA system and found that suppressing the hydrogen evolution reaction (HER) became more critical at low concentrations. We demonstrated that a Ni single-atom catalyst produced CO with high selectivity under various concentrations of CO₂. When the partial pressure of CO₂ lowered from 1.0 to 0.1 atm, Ni-N/C maintained >93% of CO Faradaic efficiency, but Ag nanoparticle showed a decrease CO Faradaic efficiency from 94% to 40%. We further developed extrinsic operating conditions controlling the water transfer inside of MEA electrolyzer and consequently, improved CO selectivity on the basis of a computational fluid dynamics simulations.