Amine-Functionalized Diamond Electrode for Boosting CO₂Reduction to CO

Carbon capture, utilization, and storage (CCUS) have been attracting much attention as an initiative to achieve carbon neutrality. In the capture and storage strategy, amines are widely used for highly efficient separation and capturing of CO₂since amines react with CO₂to form carbamates. In the utilization strategy, CO₂electroreduction is a promising method to convert CO₂into value-added compounds because reaction conditions are relatively mild and easily controlled. In this work, toward combining CO₂capture and storage technologies and CO₂electroreduction, we focused on amine modification of the electrode surface, in which boron-doped diamond (BDD) was chosen as a sustainable electrode material. CO₂electroreduction using the amine-modified BDD was performed, and an applied potential dependence of the product selectivity was examined. In situ attenuated total reflectance-infrared measurements showed that the peak intensity of the stretching vibration of the carbonyl group at around 1640 cm^-1decreased as applied potentials became more negative. The effect of amine modification of the BDD surface lies in the formation of a C-N bond during CO₂electroreduction, resulting in the enhancement of the selectivity of CO production up to 8 times compared to the unmodified BDD.