We have developed a novel catalyst, based on sputtered, oxygen-plasma-treated Ag thin films, deposited on highly hydrophobic porous PTFE substrates, for the efficient and stable CO2 electroreduction to CO. The enhanced surface defect sites and porosity of the developed catalyst, combined with the suppression of the electrolyte flooding, had a marked beneficial effect on the selectivity and stability of the CO2RR to CO. Indeed, the CO faradaic efficiency reached 90 %, maintaining a value of 80 % after 24 hours on stream, with a constant current density of around 20 mA/cm 2 , in a flow cell using mild KHCO3 electrolyte. This was achieved with only 0.18 mg/cm 2 of Ag loading, leading to high mass activity. To the best of our knowledge, this is the first example of using scalable sputter deposition of Ag on PTFE substrate, combined with plasma treatment, for the CO2 electroreduction to CO. We anticipate this approach to be applied to other metals or even to combination of metals to target C2+ products from CO2.