Reduction of carbon dioxide to methane and ethanol on the surface of graphyne-like boron nitride (BNyen) monolayer: A DFT study

Abstract

Recently, scientists have created a novel type of boron nitride material known as BNyen. This material is similar in structure to Graphyne and has a higher N:B ratio than traditional boron nitride due to the addition of boron and nitrogen connecting segments within its units. This material has been studied for its potential as a photocatalyst for reduction of CO₂ using DFT approaches. Optical and electronic attributes of BNyen suggest that it has a wider visible-light range and a band gap of 5.69 eV. By adding boron to BNyen, patial distributions of LUMO and HOMO indicate that π network has been extended, resulting in significantly greater photocatalytic efficiency. Upon the adsorption of CO₂ on BNyen monolayer, the band gap significantly decreases, indicating a strong interaction between the BNyen and CO₂. DFT computations were employed to explore the mechanism of CO₂ reduction to a single carbon product catalyzed by BNyen. Based on the ΔG values, the optimized pathway for this reduction is from CO₂ to CH₄. Additionally, the potential formation of di-carbon products was considered, and based on the free energy values, CH₃CH₂OH is identified as the final di-carbon product. The Gibbs free energies for potential CO₂ reaction pathways on BNyen were calculated, revealing that CO₂ can be reduced to CH₄ with a low limiting potential of −0.37 V and to CH₃CH₂OH with a low limiting potential of −0.57 V, both processes being powered by solar energy. In CO₂RR, the competing hydrogen evolution reaction (HER) must be considered. The free energy of HER (ΔG = 0.96 eV) is significantly higher than the ΔG of the rate-determining steps for the mono-carbon product (0.37 eV) and the di-carbon product (0.57 eV) on BNyen. Therefore, BNyen effectively suppresses HER during the CO₂RR process. This research can serve as a valuable guide for developing novel types of BNyen as appropriate photocatalysts for CO₂ reduction reactions (CO₂RR).