Thin film Ag electrodes fabrication for sustainable and high-efficiency electroreduction of CO2 to CO

The electroreduction of carbon dioxide (CO2RR) is one of the most promising ways to valorise CO2 as a source of carbon. The development of novel, efficient and scalable catalysts for CO2 electroreduction within electrolysers is still a big challenge. Here, we report the preparation of sustainable, efficient and stable gas diffusion electrodes utilizing Ag as catalyst for the CO2 electroreduction to CO. These cathodic materials are prepared by sputter deposition and subjected to post-deposition modification using dry, reactive processes. The catalyst is uniformly deposited as a thin layer on the porous structure of PTFE minimizing the amount of Ag required. This approach allows for fine tuning of the morphology, chemical composition and loading of Ag and their impact on the CO2RR. These electrodes have been evaluated for the CO2 electroreduction and for electrocatalytic studies in a flow reactor with gas-fed CO2. The optimized electrodes show high activity, with current densities > 20 mA/cm2 at -1,18 V vs. RHE, and faradaic efficiency for CO > 90 %. The stability was tested over periods up to 24 hours showing a significant impact of the post-deposition modification. Higher porosity, roughness and electrochemical surface area have been achieved after the modification. Noteworthy, our approach allows for outstanding performances using a minimal amount of metal, while using the processing advantages of sputtering as an industrial state-of-the-art, high-throughput, and roll-to-roll compatible technique. Moreover, this route enables the deposition of different metals and alloys of tailored composition for the electrocatalytic CO2 reduction beyond CO.