Electrochemically Controlled Nucleation of Single CO2 Nanobubbles via Formate Oxidation at Pt Nanoelectrodes

CO2 is an anodic product of many liquid fuel cells. The nucleation of CO2 nanobubbles during cell operation may block the transport of the fuel to the anode, lowering the overall conversion efficiency. Herein, we report the controlled formation of individual CO2 nanobubbles at Pt nanoelectrodes via the electrooxidation of formate. The electrochemical data are used to extract key parameters of CO2 gas nucleation. We determine that CO2 bubbles nucleate when the concentration of CO2 at the Pt electrode is greater than ∼0.6 M, corresponding to supersaturation of ∼18. The critical nucleus required for the formation of a CO2 bubble is measured to have a radius of curvature of ∼100 nm, a contact angle of 173°, and contains ∼70 CO2 molecules.