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

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).