Theoretical Investigation of the BCN Monolayer and Their Derivatives for Metal-free CO Photocatalysis, Capture, and Utilization.

In recent years, carbon capture and utilization (CCU) has been explored as an attractive solution to global warming, which is mainly caused by increasing CO emission levels. Many functional materials have been developed for removing atmospheric CO and converting it to more useful forms of carbon. Traditional metallic photocatalytic species have drawbacks-photocorrosion, low visible-light absorbance, and environmental damage; therefore, metal-free materials have attracted considerable research attention. In particular, boron nitride (BN) possesses unique B-N bonds, characterized by a large difference in the electronegativity of atoms that facilitates CO reduction, and catalytic CO reduction by boron carbon nitride (BCN) has been demonstrated under visible light; hence, these two materials can be considered potential CO reduction photocatalysts. However, further modification of the materials and their applicability to other CCU applications have not been extensively explored. Therefore, we decided to investigate the modification of BCN monolayers, with the aim of ensuring that the properties of the materials are better suited, first, to the requirements of CO photocatalysis, and second, to those of carbon capture or other optoelectronic applications. In this study, we considered various novel BCN monolayers, based on modification via metal-free substitutional doping and nitrogen vacancy creation, and performed first-principles density functional theory calculations. The effects of the modifications on band gap tuning, charge transfer, and the CO adsorption ability were all studied. Specifically, O-BCN and Si-2 × 2-BCN were shown to possess excellent properties for photocatalytic CO reduction, and O-2 × 2-BCN and N-4 × 4-BN can be considered for future CO capture materials. These results contribute to existing CCU approaches, suggesting that BCN monolayer modification merits further investigation, and offering insights relevant to other photocatalytic applications.