Boron site-dependent electrocatalytic CO2 reduction at the boron-doped diamond–H2O interface

Abstract

Boron-doped diamond (BDD) electrodes are highly promising candidates for electrochemical CO₂ reduction reactions (eCO₂RR). However, the specific active sites responsible for eCO₂RR on BDD electrodes remain contentious, primarily due to the limitations of traditional computational models, which overlook surface charge effects and explicit water molecules. These limitations impede the accurate characterization of the complex dynamics at the solid–liquid interface between the BDD surface and the electrolyte, presenting a significant challenge in optimizing the efficiency and selectivity of value-added product formation on BDD electrodes. In this study, we develop a BDD–H₂O explicit solvent model by substituting B atoms at surface, sub-surface, and deeply embedded C atom sites, to elucidate the nature and underlying mechanisms of the active sites in eCO₂RR on BDD electrodes under practical electrode potentials. Our computational results elucidate the reaction mechanism of formic acid formation on BDD surfaces and confirm that formic acid is the predominant reduction product under practical temperatures and potentials, consistent with previous reports. Our findings reveal that surface and subsurface B atoms in BDD are indispensable for CO₂ reduction, while deeply embedded B atoms remain essentially inactive catalytically. Furthermore, our analysis reveals that the CO produced on BDD electrodes originates from the dissociation of carboxyl groups at the surface C atoms, while formaldehyde is more likely a secondary reduction product derived from surface-adsorbed CO. This study provides crucial mechanistic insights into eCO₂RR on BDD electrodes and offers a foundation for their rational optimization, contributing to advancements in CO₂ resource utilization.