Insight into Adsorption of C₂H₂ and H₂ on Doped Graphene with Nonmetallic Atom (N, P, S): A Density Functional Theory Study.

Abstract

A DFT investigation was performed to evaluate the structure, electronic properties of the doped graphene, and the adsorption behavior of C₂H₂ and H₂ on the graphene sheet. Two kinds of doping scenarios are considered, namely dopants into pristine graphene and vacancy graphene. It is observed that the doping energy is negative for dopant (N, P, S) into vacancy graphene at pyridinictype site, yet it is positive at graphitic-type site for pristine graphene. It could be inferred that the introducing process is exothermic reaction for defective graphene. Meanwhile, for the adsorption of C₂H₂ on the surface of defective graphene, we notice that C₂H₂ would prefer to be adsorbed at the top site of the doping atom and the adsorption energy increases with the introducing of dopants, indicating that the dopant would enhance the interaction between C₂H₂ and graphene. Regarding hydrogen molecule, the dopant has less promotion effect on the adsorption. Moreover, the graphene plays a role of electron donor while the gas molecule (C₂H₂/H₂) is the electron acceptor when it is adsorbed. For the co-adsorption, the C₂H₂ is privileged to interact with the graphene and the pre-adsorbed C₂H₂ on doped graphene would weaken the opportunity of the uptake of H₂ molecule. We anticipate that our results would provide information to design the optimized catalysts.