Density functional theory-based analysis on O2 molecular interaction with the tri-s-triazine-based graphitic carbon nitride

The structural and electronic properties of O-2 molecular adsorption on the Tri-s-triazine-based graphitic carbon nitride (g-C3N4) surface was investigated through first principles calculation based on density functional theory (DFT). Here, we show that the O-2 molecule is merely physisorbed on the surface of g-C3N4 through the interaction of its lowest unoccupied molecular orbital (LUMO) with the orbitals of the 2-coordinated nitrogen atoms of the surface. Though physisorbed, a stronger molecular adsorption was found as compared with its adsorption on pure graphene sheets. We also found that the O-2 molecule gains very small amount of electron charges from the surface, which, together with a stronger adsorption energy, may attribute to a more effective oxygen reduction reaction (ORR) site as compared with pure graphene. These results would then be important for reactions with intermediate surface oxidation step in a carbon and nitrogen-based catalyst, and could lead to realization of an effective materials design for surface application, e.g. towards a more efficient catalyst for the ORR on the cathode side of the proton exchange membrane fuel cell (PEMFC). (C) 2012 Elsevier B.V. All rights reserved.