Electrocatalytic Reduction of Low Concentrations of CO2 Gas in a Membrane Electrode Assembly Electrolyzer

The direct conversion of low concentrations of CO 2 is an essential approach, considering the expensive gas conditioning process for pure CO 2, but has not yet been intensely studied in a membrane electrode assembly (MEA) electrolyzer. Herein, we explored the CO 2 reduction with various CO 2 concentrations in a zero-gap MEA electrolyzer and found that suppressing the hydrogen evolution reaction (HER) became more critical at low concentrations of CO 2 . We demonstrate that a Ni single-atom (Ni-N/C) catalyst exhibits a high tolerance toward low CO 2 partial pressure ( P CO2 ) 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 CO 2 in the zero-gap MEA. When the P CO2 was lowered from 1.0 to 0.1 atm, Ni-N/C maintained >93% of CO Faradaic efficiency (FE CO ), but Ag nanoparticles sho…