Self-Cleaning CO2 Reduction Systems: Unsteady Electrochemical Forcing Enables Stability

• Published in: ACS energy letters 2021-02, Vol.6 (2), p.809-815
• Main Authors: Xu, Yi, Edwards, Jonathan P, Liu, Shijie, Miao, Rui Kai, Huang, Jianan Erick, Gabardo, Christine M, O’Brien, Colin P, Li, Jun, Sargent, Edward H, Sinton, David
• Format: Article
• Language: English
• ISSN: 2380-8195; 2380-8195
• DOI: 10.1021/acsenergylett.0c02401

The electrochemical conversion of CO2 produces valuable chemicals and fuels. However, operating at high reaction rates produces locally alkaline conditions that convert reactant CO2 into cell-damaging carbonate salts. These salts precipitate in the porous cathode structure, block CO2 transport, reduce reaction efficiency, and render CO2 electrolysis inherently unstable. We propose a self-cleaning CO2 reduction strategy with short, periodic reductions in applied voltage, which avoids saturation and prevents carbonate salt formation. We demonstrate this approach in a membrane electrode assembly (MEA) with silver and copper catalysts, on carbon and polytetrafluoroethylene (PTFE)-based gas diffusion electrodes, respectively. When operated continuously, the C2 selectivity of the copper–PTFE system started to decline rapidly after only ∼10 h. With the self-cleaning strategy, the same electrode operated for 157 h (236 h total duration), maintaining 80% C2 product selectivity and 138 mA cm–2 of C2 partial current density, at a cost of