Janus HfSSe monolayer: a promising candidate for SO₂ and COCl₂ gas sensing

Abstract

Janus monolayers based on transition metal dichalcogenides have garnered significant interest as potential materials for nano electronic device applications due to their exceptional physical and electronic properties. In this study, we investigate the stability of the Janus HfSSe monolayer using ab-initio molecular dynamics simulations and analyze the electronic properties in its pristine state. We then examine the impact of adsorbing toxic gas molecules (AsH3, CoCl2, NH3, NO2, and SO2) on the monolayer's structure and electronic properties, testing their adsorption on different active sites on top of hafnium, selenium, and sulfur. The sensitivity of the gas molecules is quantified in terms of their adsorption energy, with the highest and lowest energies being observed for SO2 (-0.278 eV) and NH3 (-0.108 eV), respectively. Additionally, we calculate other properties such as adsorption height, Bader charge, and charge difference density to determine the sensitivity and selectivity of the toxic gas molecules. Our findings suggest that the Janus HfSSe monolayer has the potential to function as SO2 and COCl2 gas sensor due to its high sensitivity and selectivity for these two gases.