Exfoliated MoS 2 Temperature programmed desorption

Abstract

The adsorption sites on MoS 2 have been studied using the temperature programmed desorption (TPD) technique. Room temperature adsorption of CO 2, CO and O 2 on this powdered material and on its exfoliated forms (in some cases supported on alumina), revealed three distinct desorption peaks for CO 2 and two for both CO and O 2, each corresponding to a particular adsorption site. We suggest from the results that the low temperature peak of CO 2 respresents the sites on basal planes of single layered crystallites, the medium temperature peak is due to the sites on basal planes of multilayered crystallites and the high temperature peak represents the general active sites on MoS 2 and/or sites on the alumina support. The low temperature CO peak is believed to be from oxygen sites on the edges of single layered crystallites, while its high temperature peak represents both the sulfur sites and the oxygen-related sites on these edges. We conclude the low temperature O 2 peak is due to the edges of single layered crystallites and its high temperature one represents the sites on the edges of multilayered crystallites. With these interpretations the form of the MoS 2 after various treatments can be suggested. The coverage of the above gases, in terms of effective surface area for room temperature adsorption, is also presented.