Influence of Pd/Pd2 decoration on the structural, electronic and sensing properties of monolayer graphene in the presence of methane molecule: A dispersion-corrected DFT study

Abstract

This paper is devoted to study on the methane (CH4) adsorption ability of graphene decorated by a single palladium (Pd) atom and its dimer (Pd2), using dispersion-corrected density functional theory (DFT-D2). The adsorption energy, optimum geometry and electronic structure in terms of density of states, band structure, and charge transfer are calculated. Our results show that van der Waals interactions lead to physisorption of CH4 on the prisitine graphene with the adsorption energy of −112 meV, which is close to its experimental value. The calculations also show that hybridization of Pd and graphene electronic states strongly binds Pd atoms to graphene surface, inducing chemisorption of the adsorbate. The adsorption energies of Pd atom and its dimer have been found to be −1.43eV and −2.27eV, respectively. Furthermore symmetry breaking of the graphene structure, due to the Pd/Pd2-decoration, leads to opening a band gap, bringing graphene from semimetalic to semiconducting state. In the presence of methane molecule, the electronic band gap of Pd-decorated graphene is increased from 73 meV to 90 meV, while for Pd dimer it is decreased from 185 meV to 55 meV. As a result, compared to Pd-decorated graphene, Pd2-decorated graphene has a stronger interaction with the methane molecule and may provide a more sensitive signal for methane gas detection.