Toward enhanced combustion gas monitoring and capture: sulfur vacancies as vectors for selective CO and CO2 intercalation in MoS2

Abstract

Molecular intercalation holds significant implications for the effective utilization of two-dimensional (2D) materials in a wide array of key applications, including gas detection and catalysis. However, its full potential remains underexplored. Using density functional theory (DFT) simulations, this study examines the intercalation of carbon monoxide (CO) and carbon dioxide (CO₂) into molybdenum disulfide (MoS₂) and the impact of sulfur vacancies on the process. Our findings reveal that CO intercalation is universally unfavorable in pristine MoS₂, while CO₂ intercalation is marginally favorable only at high molecular coverages. Sulfur vacancies, however, serve as selective vectors, facilitating CO intercalation by incorporating CO molecules into the vacancy sites and enabling catalytic CO-to-CO₂ conversion without significantly affecting CO₂ intercalation. The extent of enhancement in CO intercalation correlates with the vacancy concentration, highlighting the potential of defect engineering in MoS₂ for a number of potential applications. This mechanism offers a promising approach for CO detection in CO + CO₂ gas mixtures, which combines an intrinsic feedback loop for elevated gas capture in MoS₂ under conditions of incomplete combustion. Additionally, sulfur vacancies support CO oxidation back to CO₂, suggesting new opportunities for the CO₂ reduction reaction (CRR) and advancing the design of multifunctional catalytic systems based on 2D materials.