Surface Modification of Sputtered, Thin-Film Silver Electrodes for Sustainable and Highly Efficient Electroreduction of CO ₂ to CO

The electrochemical carbon dioxide reduction reaction (CO 2 RR) is one of the most promising ways to valorize CO 2 as a source of carbon. The development of efficient and scalable catalysts for CO 2 electroreduction in electrolyzers is still a big challenge. This paper reports on the preparation of sustainable, efficient, and stable gas diffusion electrodes utilizing silver as the catalyst for the CO 2 electroreduction to CO. The catalyst is prepared by sputter deposition and subsequent surface modification by oxygen plasma. It is uniformly deposited as a thin layer on the hydrophobic porous structure of polytetrafluoroethylene (PTFE), minimizing the amount of silver required and simultaneously addressing the problem of substrate flooding by the electrolyte. This leads to a synergetic, beneficial impact on the CO 2 RR, as evaluated in a flow reactor with gas-fed CO 2 . The optimized gas diffusion electrodes, with high porosity and electrochemical surface area, show high activity at low overpotentials, faradaic efficiency for CO over 90%, and stability tested over periods up to 24 h. This approach allows for high performance using a minimal amount of metal while exploiting the processing advantages of sputtering as an industrial state-of-the-art, high-throughput technique.