Nanobubble-infused electrolytes for enhanced mass transfer in liquid-fed CO2 electroreduction.

Electrochemical carbon dioxide reduction (CO₂RR) in aqueous systems provides a sustainable pathway to convert CO₂ into valuable chemicals and fuels. However, the limited solubility and slow diffusion of CO₂ in aqueous electrolyte impose significant mass transfer barriers, particularly at high current densities. This study introduces a nanobubble-infused electrolyte strategy that leverages the unique properties of nanobubbles, including localized CO₂ enrichment, enhanced diffusion, and micro-convection to overcome these limitations. Compared to conventional CO₂-saturated electrolytes, the nanobubble-infused electrolytes achieve a 10-fold increase in the volumetric mass transfer coefficient and a 42.3% increase in the limiting current density. Implementing this approach with a zero-gap liquid-fed electrolyzer featuring a hydrophilic diffusion medium further enhances mass transfer, yielding an additional 28% increase in limiting current density. Mechanistic insights from multiphysics simulations reveal that nanobubbles enhance CO₂ availability near the catalyst, reduce overpotentials, and improve CO₂RR selectivity by suppressing hydrogen evolution. By validating this scalable and robust approach across different catalysts, this work establishes nanobubble-infused electrolytes as a universal solution for addressing mass transfer challenges independent of catalyst choice in liquid-fed CO₂RR and paves the way for industrial-scale CO₂ conversion technologies.