Rigorous assessment of CO2 electroreduction products in a flow cell

Abstract

Electrochemical conversion of carbon dioxide (CO₂) into valuable carbon-based chemicals provides a route to store renewable electricity and close the carbon loop. In comparison to the conventional “H-cells”, the flow-cell reactors enable CO₂ reduction reaction (CO₂RR) operating at much higher current densities via mitigating the mass-transport limitation issue. However, the lack of a standard testing methodology has led to inaccurate detection of CO₂RR products and thus unfair performance comparisons. Herein, we identified several commonly overlooked aspects in terms of product measurements during CO₂ electrolysis in flow cells, which could cause a considerable misestimation even up to a ratio of 45% in certain scenarios. Systematic experiments suggest a modified flow-cell testing system that permits the establishment of benchmarks by which CO₂RR products can be accurately assessed. Our study, for the first time, offers a rigorous protocol towards the accurate measurement of both gas and liquid CO₂RR products in flow cells.