Effect of Fe and point deficiency on adsorption behavior of NH₃ on coke surface: A density functional theory study

Effect of Fe and point deficiency on adsorption behavior of NH₃ on coke surface was studied using density functional theory and graphene model with periodic boundary conditions. The results show that the adsorption of NH₃ on surface of point-defective graphene belongs to physical adsorption with binding energy of -0.381 eV. The adsorption of NH₃ on surface of Fe-modified-graphene belongs to chemical adsorption with energy of -1.442 eV. The adsorption energy of NH₃ in the presence of Fe atom or point defect is greater than that of NH₃ on the surface of intact graphene. In addition, coexistence of Fe atom and point defect has a synergistic effect on adsorption of NH₃ with binding energy of -3.538 eV, which is much higher than the sum of adsorption energy of NH₃ in the presence of the two alone. There is more charge transferring among Fe atom, graphene surface and NH₃ molecule, which can explain the synergistic effect of coexistence of Fe and point defect.