Electrochemical reaction of CO to CO on a catalyst coated cation exchange membrane enabled by ammonium proton shuttling

• Published in: Catalysis science & technology 2022-10, Vol.12 (19), p.5829-584
• Main Authors: Reinisch, D, Reichbauer, T, Vetter, K. M, Marti, N, Mayrhofer, K. J. J, Schmid, G
• Format: Article
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/d2cy00878e

CO 2 reduction (CO 2 RR) can convert CO 2 into feedstock for the chemical industry. In aqueous CO 2 electrolysis a key challenge is how to combine the CO 2 educt with a neutral or alkaline electrolyte and achieve a stable cell operation. We propose a novel cell design and operation mode based on a catalyst coated cation exchange membrane: a cationic acid (NH 4 + ), with a volatile conjugate base (NH 3 ), replaces the protons usually present for ion transport. The approach avoids a high proton concentration at the cathode catalyst while still removing all products within the gas phase. In this paper different cell concepts are investigated to identify a pathway to a stable, efficient and scalable operation mode. In a completely novel cell design a FE CO > 50% was already maintained for over 35 h at 50 mA cm −2 , and at 200 mA cm −2 a cell voltage of 3.6 V (FE CO > 60%) was achieved. Surprisingly, ammonium oxidation at the anode was fully supressed under the reaction conditions. CO 2 reduction (CO 2 RR) can convert CO 2 into feedstock for the chemical industry. In a novel operation mode NH 4 + ions locally buffer the pH on a cation exchange membrane (CEM) and thereby enable efficient CO 2 RR on an Ag-coated CEM cathode.