Unique properties of fine bubbles in the electrochemical reduction of carbon dioxide using boron-doped diamond electrodes

The electrochemical CO₂ reduction on boron-doped diamond (BDD) electrodes in an aqueous solution with fine bubbles was studied. The overpotential decreased and the production of carbon monoxide was promoted in the CO₂ reduction with fine bubbles compared to that without fine bubbles. It is suggested that fine bubbles in solution could facilitate the mass transport and also act as the catalyst for producing carbon monoxide. Potential-dependent in-situ attenuated total reflectance-infrared (ATR-IR) measurements confirmed the catalytic activity, showing that in solutions with CO₂ fine bubbles the CO₂^•– intermediate or the CO₂ molecules themselves become stabilized near the electrode and these can be adsorbed on the electrode surface more easily compared to using solutions without CO₂ fine bubbles. The reported work is a first step in understanding the effects of fine bubbles in CO₂ reduction reactions.