A membrane electrode assembly-type cell designed for selective CO production from bicarbonate electrolyte and air containing CO2 mixed gas

Abstract

The electrochemical CO2 reduction reaction (CO2RR) combined with direct air capture (DAC) based CO2 is a promising method for terrestrial carbon cycling. In this study, we have designed an all-Ag cathode and constructed a membrane electrode assembly (MEA) cell to utilize CO2 capture solution, which can be produced by flowing air containing CO2 mixed gas into an alkaline solution. A MEA consisting of a Ag nanoparticle catalyst sprayed on a Nafion membrane and a Ag electrode were used to construct a MEA cell (Ag MEA-cell). The Ag MEA-cell exhibited selective CO production without severe side reactions, such as the hydrogen evolution reaction, even when an aqueous electrolyte was used. The operation of the Ag MEA-cell using CO2 capture solution, which was prepared by bubbling 60% air containing CO2 mixed gas (40% CO2 and 60% air, air-CO2) into 1 M KOH, achieved CO production with 86% faradaic efficiency (FECO). Furthermore, the Ag MEA-cell significantly suppressed O2 reduction and achieved FECO of 74% even when air-CO2 was used as a CO2 source.