First principles study on the functionalization of graphene with Fe catalyst for the detection of CO2: Effect of catalyst clustering

The surface functionalization of graphene plays an important role in the development of graphene-based sensors for gas detection and removal. Here, we report the effect of decoration of graphene with Fe catalyst, as either scattered adatoms (Fe-adatoms@G) or clustered (Fe-cluster@G) on the detection of CO2 gas molecule and its influence on the structural, adsorption, electronic and magnetic properties of graphene using the spin-polarized density functional theory (DFT). The results show that the adsorption of scattered Fe-adatoms and Fe-4-cluster on graphene would break the degeneracy of spin-up and spin-down states, resulting in ferromagnetic adsorptionbed for the detection of CO2 molecules. The magnetic moment of Feadatoms@G remains the same for all concentration of CO2, while the magnetic moment of Fe-cluster@G decreases from 10.03 mu B to 4 mu B by increasing the concentration of CO2 from one to four molecules. It is found that the scattered Fe-adatoms on graphene have the higher tendency to adsorb more CO2 molecules than that of the cluster with the same number of Fe atoms, whereas Fe4-cluster on graphene detects CO2 molecules using magnetism. Our results have indeed a direct application to fabricate solid-state and magnetic-based gas sensors using graphene to detect CO2 gas molecules.