The insensitive cation effect on a single atom Ni catalyst allows selective electrochemical conversion of captured CO2 in universal media

Abstract

The direct electroconversion of captured CO2 is attracting attention as a streamlined manner for carbon capture and utilization, omitting energy-demanding CO2 separation processes. In amine-based conventional capturing media, however, the reaction inevitably takes place in the presence of bulky ammonium cations, leading to low charge density on the electrode surface and consequent inferior reactivity. Hence, discovering cation-insensitive electrode materials is of prime importance to electrochemically activate the captured CO2, but has not yet been explored. Here, we report that a single atom Ni catalyst embedded on N-doped carbon (Ni-N/C) exhibits weak cation sensitivity, which allows a notably high CO selectivity (64.9%) at -50 mA cm(-2) integrated with a membrane electrode assembly in a CO2-capturing monoethanolamine-based electrolyte. Moreover, the weak cation sensitivity of Ni-N/C enables it to exhibit universally high CO selectivity even in a bulkier electrolyte, whereas the Ag catalyst shows a decrease depending on the type of amine. We propose that the positively shifted potential of the zero charge of Ni-N/C enables the high surface charge density to be maintained even in the presence of bulky cations, allowing high CO production activity in various capturing solutions. These trends provide insights into selective catalyst design for the electroconversion of captured CO2 in universal media.