Anisotropic CO adsorption and enhanced O2 activation on defective TiS2 monolayer: A DFT study

Abstract

This study employs density functional theory (DFT) calculations to investigate the adsorption behaviour of CO and O2 on a defective TiS2 monolayer. The primary objective is to evaluate the potential of TiS2 for gas sensing and catalytic applications. By exploring the adsorption of CO and O2 on a monolayer with a sulfur vacancy, this study provides significant new insights into their interaction mechanisms and energetics. The DFT simulations showed that the adsorption of the CO molecule is anisotropic (i.e., orientation dependent) with higher adsorption energy for the carbon end (Ti-CO) -0.63 eV than the oxygen end (Ti-OC) -0.16 eV. In both scenarios, the CO molecule bond length does not change significantly. In contrast, the adsorption of O2 molecule is the strongest with the highest adsorption energy of -3.25 eV. The defective TiS2 monolayer exhibits notable catalytic properties through the elongation of the O-O bond from 1.21 Å to 1.47 Å, comparable to the O-O bond length in peroxides (∼ 1.45 Å). Additionally, the adsorption mechanism is explained in variation observed in Density of States (DOS), Partial Density of States (PDOS), and Mulliken charges, thus establishing its potential for gas sensing and catalytic applications.