Engineering of 2d Mos2 for Improved Gas Sensing, Heavy Metals Capture and Hydrogen Harvesting: an Ab Initio Study

Abstract

Two-dimensional molybdenum disulfide (2D MoS2) is a promising material for applications in greenhouse gas (GHG) sensing, photocatalytic water splitting, and heavy metal (HM) removal from water. However, the fundamental principles behind doping this material with non-metallic elements remain unexplored, yet gaining a deeper understanding in this area could open up new opportunities to further enhance these capabilities. Here, density functional theory and molecular dynamics simulations were employed to investigate the effects of X atom dopants (O, Cl, P, and Se) on the structural and electronic properties of 2D MoS2 and their applications in GHG sensing, photocatalytic water splitting, and HM adsorption. It is found that under non-equilibrium conditions, X elements could be integrated into the lattice of 2D MoS2, with chlorine (Cl) exhibiting the highest and selenium (Se) the lowest formation energies. Surface distortions induced by Se and O elements included protrusion and depression, respectively, while P and chlorine (Cl) caused minimal distortion. Additionally, P and Cl doping narrowed the band gap and increased charge densities, while O and Se had minimal effects. Regarding GHG sensing, X-doped 2D MoS2 exhibited potential as a GHG sensor, with Cl, O, and P-doped materials showing selectivity and sensitivity to CO2, CH4, and N2O, respectively. Charge transfer analysis revealed electron exchanges during adsorption, influencing the material's electrical conductivity and correlating with gas concentration. Thermal treatment allowed for gas desorption, converting the material to a reusable state, with Cl-doped 2D MoS2 showing superior performance in CO2 sensing. In terms of photocatalytic activity, X-doped 2D MoS2 demonstrated potential for harvesting solar energy, especially with Cl and P dopants, which widened the absorption spectrum. P-doped 2D MoS2 emerged as a superior photocatalyst due to its optimized band gap alignment, enhancing catalytic ability. For HMs removal, P- and Cl-doped MoS2 surfaces showed favorable interactions with HMs compared to Se and O-doped systems, with Cl-doped MoS2 proving effective in removing Hg, Cd, and Zn due to moderate adsorption energies. Analysis of projected density of states revealed hybridization of electrons, and thermal treatment expelled HMs from Cl-doped 2D MoS2 surface, rendering the material reusable. This study highlights the potential of X-doped 2D MoS2 in environmental applications, offering insights for future research and development.