Theoretical Study of ZnS Monolayer Adsorption Behavior for CO and HF Gas Molecules

Abstract

Adsorption of carbon monoxide (CO) and hydrogen fluoride (HF) gas molecules on a ZnS monolayer with weak van der Waals interactions is studied using the DFT + U method. From our calculation, the ZnS monolayer shows chemisorption with CO (E ads = −0.96 eV) and HF (E ads = −0.86 eV) gas molecules. Bader charge analysis shows that charge transfer is independent of the binding environment. A higher energy barrier for CO when migrating from one optimal site to another suggests that clustering may be avoided by the introduction of multiple CO molecules upon ZnS, while the diffusion energy barrier (DEB) for HF suggests that binding may occur more easily for HF gas upon the ZnS ML. Adsorption of the considered diatomic molecule also results in a significant variation in effective mass and therefore can be used to enhance the carrier mobility of the ZnS ML. Additionally, the calculation of recovery time shows that desirable sensing and desorption performance for CO and HF gas molecules can be achieved at room temperature (300 K).

Highly sensitive sensing of CO and HF gases by monolayer CuCl

“…It is calculated that the charge transfer between the HF and CuCl monolayer is −0.04 e , which is a bit greater than that in previous studies, 35 and similarly we observed a high charge transfer of 0.03 e for the CO/CuCl ML as compared to that in previous studies. 30,32–35 It is observed from the calculations that the charge transfer is independent of the Hubbard parameter, i.e. , the local binding environments, and only relies upon the properties of the adsorbed gas and the nature of the monolayer, which is compatible with the findings of previous studies.…”

“…It is observed that at RT, the value of the recovery time of CO on CuCl ML is 1.69 × 10 18 s, while HF molecules show a more rapid recovery time of 1.09 × 10 −7 s, which is much less than that found in previous studies on HF (4.68 min). 34 This indicates that we can achieve active sensing with a fast recovery time for HF at RT (300 K). 56,57 Further calculations are carried out to determine the changes with various temperatures.…”

“…So, it is concluded that the CuCl ML shows a very good adsorption performance for CO gas molecules in comparison with that of other substrates in previous studies, like InN (−0.223 eV), phosphorene (0.325 eV), Janus Te 2 Se (−0.171 eV), graphene (P-graphene, −0.12 eV; Bgraphene, −0.14 eV; N-graphene, −0.1 eV), and monolayer ZnS (−0.96 eV), as well as pristine hBN (0.21 eV) and Ti-doped hBN (1.66 eV). [30][31][32][33][34][35] Meanwhile, the HF molecule shows physical adsorption to the CuCl ML, with a smaller physical adsorption energy of −0.31 eV. Even so, the CuCl monolayer shows a better adsorption energy for HF molecules as compared to that of Ti-doped hBN, 0.27 eV.…”

“…Recent studies also demonstrated HF and CO adsorption. 34,35 N. Ahmadian et al discovered an appropriate and sensitive sensor for dimethyl methylphosphonate (DMMP, a nerve agent) on the exterior surface of defect-containing semiconducting (10,0) single-wall carbon nanotubes (SWCNTs), by using first-principles van der Waals density functional (vdW-DF) calculations. 36 M. D. Ganji et al studied the adsorption of formaldehyde (H 2 CO) on graphene, hexagonal silicon carbide (h-SiC) and hexagonal aluminum nitride (h-AlN) monolayer sheets for application as gas sensors.…”