Exploring and Elucidating the CO₂ Reduction Mechanisms on the Surface of Two-Dimensional Nitrogen-Vacancy (V_N) Hexagonal Boron Nitride

The conversion of waste carbon dioxide (CO2) gas into valuable products and fuels through an electrocatalytic CO2 reduction reaction (CO2RR) is a promising approach. The sluggish kinetics of the CO2RR require the development of novel strategies for the electrocatalyst design. Two-dimensional (2D) materials emerge as promising candidates for the CO2RR due to their distinctive electronic and structural properties. This study follows the first-principles–based DFT-D method to examine the electrocatalytic competences of the defective two-dimensional boron nitride monolayer (d-BN) material toward the CO2RR. Introducing a particular defect with nitrogen vacancies in 2D single-layer pristine hexagonal boron nitride (VN_d-BN) can efficiently activate the CO2 molecules for hydrogenation by reducing the electronic band gap of pristine hBN from 6.23 to 3.0 eV. Therefore, the VN_d-BN material can act as a large band gap semiconductor. Our findings demonstrate that the defective regions in 2D monolayer VN_d-BN serve as active sites (boron) for both the adsorption and activation of CO2. The subsequent hydrogenation steps occur sequentially once the CO2 molecule is adsorbed on the catalytic surface. Our results indicate that the OCHO* path is the most favorable for CH4 production. Hence, the 2D monolayer VN_d-BN material holds a great promise as a cost-effective catalyst for the CO2RR, and it presents a viable alternative to expensive platinum (Pt) catalysts.