Chemical Bonding and Electronic Properties of the Co Adatom and Dimer Interacting with Polyaromatic Hydrocarbons

Abstract

The density functional calculations presented here elucidate the nature of the interaction between the Co atom and dimer with a polyaromatic hydrocarbon (PAH). The results are analyzed in terms of structural, electronic and magnetic properties. The bonding character of the Co atom and dimer adsorbed on the PAH exhibits a strong covalent bonding, arising from a hybridization between the d orbitals of Co and the p z orbitals of the carbon atoms, which cause an in-plane distortion in the PAHs. A small charge transfer takes place from the Co atom and dimer to the PAH surface, which creates a positive charge on the metal atoms and thereby change their catalytic activity. Upon adsorption, the magnetic moment of the Co adatom is reduced depending on the adsorption site. For the perpendicular Co dimer to the PAH plane, the projected magnetic moment of the Co atom further from the PAH is increased, which is due to antiferromagnetic coupling between the Co atoms in this configuration. Density of state analysis shows that the main contribution of magnetic moment reduction is due to promotion of electrons from the 4s states to the 3d states of the Co adatom upon adsorption.

Influence of Carbon Support on Electronic Structure and Catalytic Activity of Pt Catalysts: Binding to the CO Molecule

“…This computational approach has been successful to describe the Pt/C and Co/C interactions. [16][17][18] The calculations were carried out using a polycyclic aromatic hydrocarbon (PAH) molecule as a representative example for modelling a real graphene material, since bonding to PAHs represents a model for binding to the π system relatively near defects in a real graphene material. Several PAH models were investigated in our previous work and the C 54 H 18 molecule was found to be a suitable model system.…”

“…13,14 Interfaces between transition metals (TM) and graphene have been investigated extensively by several theoretical and experimental techniques. [16][17][18][19][20][21][22] Müller et al investigated a single Pt atom, Pt dimers and trimers on highly oriented pyrolytic graphite using a scanning tunneling microscope (STM) in air. 21 The Pt particles were produced by evaporation of platinum onto the surface and the position of the Pt atoms were stable, without changes for many scans.…”

Adsorption and growth of palladium clusters on graphdiyne

“…Often, clusters of transition metals (TM) supported on appropriate surfaces are the active catalysts, and the understanding of the cluster-support interaction is of great scientific and technological interest. Also, for many other purposes, the presence of adsorbed clusters can modify the electronic and magnetic properties of the substrate system 1 . There are some challenges regarding the adsorption of molecular species on supported metal clusters, related to the coupling of the clusters with the substrate [2][3][4][5][6][7][8][9] .…”

DFT study of the coverage-dependent chemisorption of molecular H 2 on neutral cobalt dimers

“…Another detection method less sensitive maybe based on the quenching of the magnetic moment of the Co2 clusters upon H2 adsorption. A recent DFT study showed that magnetic moment of two PAH-supported Co atoms is smaller than that of the end-on adsorbed dimer [27], therefore our calculations suggest that a sensor material based on Co2 rather than Co would be more sensitive. These rather technical aspects could become relevant for the design of functional conductive paramagnetic materials functionalised with Co2, which was recently shown to bind to graphene while preserving the magnetic properties of the cluster [46].…”

“…Magnetization measurements have shown considerable size-dependence of the magnetic moment in clusters with smaller clusters having higher magentic moments [26]. Therefore, the presence of high magnetic moments in small cobalt clusters such as Co2 and the possibility of funtionalising them to graphene sheets [27], makes them ideal for the development of novel materials for H-sensors or other megneto-electronic apllications in nanotechnology. There have been a few recent reports that have applied bimetallic [28] (e.g.…”