Structure Of Nitrogen-inclusive Graphene And Synergistic Reaction Mechanism Study On Its Metal Supported Catalysts

Two main disadvantages existed in employment of Pt electrode for fuel cell. They are low storage and high price, and easily be poisoned by CO during the process.In order to improve shortcomings mentioned above, we developed modified Pt based catalyst and non-Pt based catalyst, which could decrease usage of Pt and relief poisoning by CO drastically.First-principles spin polarized density functional theory(DFT) calculations was employed, we investigated structures and electronic properties of ‘‘external’’ nitrogen modified graphene, and oxygen reduction reaction(ORR) catalytic mechanism of Au&Pt nanotube supported catalysts and Co4 N supported N-doped graphene catalysts.Calculation results showed:(1) in the most stable structures, the bonding between pyridine derivatives and graphene involves the ortho-carbon of pyridine derivatives, as confirmed by the Bader charge analysis. The enhanced stability of pyridine derivatives on graphene by [2+2] cycloaddition, e.g., a double bonding mode(DBPyNG), is caused by the matches between frontier orbitals of pyridine derivatives and those of graphene, which leads to the formation of stronger chemical bonds. Interestingly, electronic structure density of states(DOS) analysis of SBPyNG reveals that the spin-up and spin-down parts are clearly split while it is not the case for the double bonding pyridine derivative modified graphene(DBPyNG).(2) ORR catalyzed by AuPt nanotube supported pyridine alkyne graphene(AuPt&PyNG) adapted to both 2e and 4e mechanism. Structure analysis told that the adsorption of OH* was stronger than that of O* or OOH*. Charge transfer showed that adsorption structures of ORR intermediateswere reasonable and adsorption state of OOH* was existed.From Gribbs free energy thermodynamics analysis we learned that the generation of OH*was rate-determining step. Moreover, 2e mechanism was more attainable than 4e for this catalysis system.(3)Two absolutely different nitrogen active sites in cobalt nitride supported N-doped graphene(Co4N/NG) catalysts could improve ORR properties significantly.Doping of N into graphene sheet could improve its ORR activity for the reason that adsorption of intermediates were weaken so that ORR performed more easily. Subsequently, Co4N/NG, which adapted to 4e mechanism was demonstrated by thermodynamics, could further improved ORR property.Our calculation results explained occurrence in experiments perfectly and provide theory support for developing catalysts with low cost buthigh activity and stability.