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.