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.