Gas adsorption on MoS2 monolayer from first-principles calculations (1306.6751v1)

Abstract: First-principles calculations within density functional theory (DFT) have been carried out to investigate the adsorption of various gas molecules including CO, CO2, NH3, NO and NO2 on MoS2 monolayer in order to fully exploit the gas sensing capabilities of MoS2. By including van der Waals (vdW) interactions between gas molecules and MoS2, we find that only NO and NO2 can bind strongly to MoS2 sheet with large adsorption energies, which is in line with experimental observations. The charge transfer and the variation of electronic structures are discussed in view of the density of states and molecular orbitals of the gas molecules. Our results thus provide a theoretical basis for the potential applications of MoS2 monolayer in gas sensing and give an explanation for recent experimental findings.

• The paper demonstrates that vdW interactions significantly boost adsorption energies, with NO and NO₂ binding much stronger than CO, CO₂, and NH₃.
• It employs DFT with PAW methods and advanced vdW correction schemes to capture key electronic modifications and charge-transfer effects during gas adsorption.
• The findings highlight MoS₂ monolayers’ promising potential for sensitive gas detection, suggesting they may outperform graphene-based sensors for toxic gases.

Gas Adsorption on MoS₂ Monolayer from First-Principles Calculations

This paper presents a comprehensive investigation of gas molecule adsorption on a molybdenum disulfide (MoS₂) monolayer by deploying first-principles calculations within the framework of Density Functional Theory (DFT). The research analyzes the binding energies and electronic interactions between the MoS₂ surface and various gas molecules including CO, CO₂, NH₃, NO, and NO₂, while accounting for van der Waals (vdW) interactions to achieve more accurate simulation results. The fundamental aim is to ascertain the potential of MoS₂ monolayers as efficient gas sensors, a utility that could be valuable in industrial and public health contexts given the pertinence of detecting toxic gases.

Computational Methodology and Results:

The authors employ DFT calculations using the Vienna Ab initio Simulation Package (VASP) alongside projector-augmented wave (PAW) methods. The computations are performed on a 5x5x1 supercell of the 1H-MoS₂ monolayer. Both DFT-D2 and vdw-DF methods, incorporating exchange-correlation energies through optPBE and revPBE functionals, are utilized to account for vdW interactions.

Key findings reveal that without vdW interactions, the adsorption energies for CO, CO₂, and NH₃ are relatively small, indicating weak interactions with the MoS₂ monolayer. Conversely, NO and NO₂ exhibit strong binding energies. With vdW interactions considered, the adsorption energies notably increase, particularly for NO and NO₂, suggesting these gases bind robustly to the MoS₂ surface compared to CO, CO₂, and NH₃. These strong interactions imply potential practical applications in detecting NO and NO₂.

The paper further elucidates the electronic structure modifications due to gas adsorption by analyzing total and spin-polarized density of states (DOS). Notably, the adsorption of magnetic molecules like NO generates distinct electronic state alterations, including n-type doping for NO, indicating a notable charge transfer from the monolayer. The charge analysis, bolstered by Bader charge calculations, ascertains that NO acts primarily as an electron acceptor, altering the conductivity of the MoS₂ monolayer.

Theoretical and Practical Implications:

The findings substantiate the theoretical models predicting gas adsorption impacts on electronic configurations of 2D materials and offer theoretical backing for potential MoS₂-based gas sensing applications. The pronounced affinity of NO and NO₂ to MoS₂ can be attributed to strong vdW contributions and charge-transfer mechanisms, suggesting that MoS₂ monolayers may outperform traditional graphene-based sensors in specific scenarios involving oxidizing gases like NO₂.

Future Research Directions:

Research could further explore the integration of MoS₂ in practical sensor devices, focusing on factors such as operational stability, selectivity, and the influence of ambient environmental conditions. Additionally, experimental verification of computational predictions remains crucial, emphasizing the need for experimental adsorption studies to confirm computational insights, particularly pertaining to vdW-dominated systems.

In conclusion, the paper provides critical insights into the sensing capabilities of MoS₂ for certain gases, emphasizes the importance of vdW interactions in accurately predicting adsorption characteristics, and lays the groundwork for further exploration of 2D materials in sensor technology.