Surface Modification of Sputtered, Thin-Film Silver Electrodes for Sustainable and Highly Efficient Electroreduction of CO2 to CO

The electrochemical carbon dioxide reduction reaction (CO2RR) is one of the most promising ways to valorize CO2 as a source of carbon. The development of efficient and scalable catalysts for CO2 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 CO2 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 CO2RR, as evaluated in a flow reactor with gas-fed CO2. 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.