Insight the process of hydrazine gas adsorption on layered WS 2 : a first principle study

The process of hydrazine gas adsorption on layered WS has been systematically studied from first principle calculations. Our results demonstrate that this adsorption process is exothermic, and hydrazine molecules are physically adsorbed. The layer-dependent adsorption energy and interlayer separation induced by van der Waals interaction exerted by hydrazine molecules lead to the difficulty in desorbing hydrazine molecules from layered WS as the number of layers increases. The most interesting finding is the emergence of localized impurity states below the Fermi level upon the hydrazine adsorption, irrespective of the number of WS layers, resulting in a significant effect on the band structures and subsequently changing its electrical conductivity. Furthermore, a layer-dependent small charge transfer occurs between hydrazine and layered WS , leading to a charge redistribution and considerable polarization in the adsorbed systems. The existence of defects and the humidity, on the other hand, influences the sensitivity of layered WS to the hydrazine adsorption. Obtained results show that a perfectly layered WS might be a promising candidate as an efficient nanosensor to detect such toxic gas in dry environment.