Structural transition of VSe2 on Au(1 1 1) induced by high sensitivity to CO gas

Abstract

Carbon monoxide (CO) is one of the well-studied reactants in many chemical catalytic reactions, and it is important to deeply understand the adsorption behavior as well as chemical reactivity of CO on a solid surface with regards to adsorption/desorption kinetics. Therefore, it is of great interest to study the process of CO adsorption and further catalytic reaction on one of the transition metal dichalcogenides, namely Vanadium diselenide (VSe2) because of its excellent catalytic activities. Herein, based on in-situ scanning tunneling microscopy (STM) study and density functional theory (DFT) calculations, we systematically investigated the absorption effect under different CO pressures. At relatively low pressure of CO (about 1x10-8 mbar), a few CO molecules adsorb on VSe2 and lead to the desorption of the top-Se atoms resulting in point defects. With the rise of pressure, the amount of absorbed CO increases, and the underlying V atoms also desorb due to the interaction of CO, finally leading to the structural transition of the whole VSe2. One thing to note is that, during the experiment CO atmosphere was injected as a continuous flow and some STM images were taken at the same time expressing the dynamic behavior of CO adsorption on VSe2, which has scarcely been in other static systems like UHV-STM.