| Since the discovery of graphene in2004, it has attracted tremendous research interest dueto its unique geometrical structures and excellent physical and chemical properties. Recently,a large number of investigations have shown that graphene which has large surface areas andunique electrical properties, is capable of preparing metal-graphene complexes as highperformance carbon based gas storage materials, sensoring platforms, catalysts and so forth.However, due to the tiny size of graphene and metal nanoclusters, it is very difficult tocharacterize these nanocomposites and measure their properties by experiment, so the methodof molecular simulation has much more advantages. In this article, we mainly discuss theinteraction between different gas molecules and metal-doped graphene through DensityFunctional Theory (DFT) simulation, the main purpose of this article is to uncover the generalmeahanisms of the interaction between different gas molecules and metal-doped graphene.Firstly, using the dmol3module embedded in the Materials Studio (MS) software, weinvestigate the influence of O2molecule on the hydrogen (H2) storage process of metal dopedgraphene. It shows that, for Ti-doped graphene, O2has a large impact on its H2storageprocess. The O2molecule could interferes with the H2adsorption process by blocking theadsorption site and irreversible oxidation of the Ti atom. The average adsorption energyE H2for H2adsorbed onto the surface of Ti-doped graphene could be droped by2/3after O2isintroduced into the system. Besides, for H2coadsorbed with O2, each Ti atom can only adsorb2H2molecules with a theoretical H2storage capacity of1.82%. So Ti-doped graphene can notfulfill the need of high performance hydrogen storage material. For Li-doped graphene,though the final geometric morphologies for H2adsorbed onto Li-doped graphene are greatlyinfluenced by the O2molecule, the adsorption enery doesn’t decrease after O2isintroduced. Under the condition of coadsorption, each Li atom can still adsorb4H2molecuels,and the theoretical hydrogen storage capacity is about7%, Li-doped graphene can still act asexcellent hydrogen storage material under the influence of O2. Our research indicates that wehave to take the influence of O2and other competitive gas into consideration whileinvestigating the hydrogen storage materials.After that, we study the effect of an external electric field on the interaction between O2molecule and Au-doped graphene. Compared with that without an electric feld, the interaction between the two would be strengthened under a negative electric field, theadsorption energyE adcould be increased by more than90%under1.5V/; whilegradually decreases by30%under a positive electric field. From the point of―internal electricfield‖and―external electric field‖, we can give possible explaination as follows, after O2adsorbed onto Au-doped graphene, the electrons flow from defective graphene substrate up tothe adsorbed O2molecule, O2acts as the donator on the graphene substrate. Thecorresponding internal electric field is pointing downward which correspond with thedirection of the negative electric field, so the interaction would be strengthened under anegative electric field, the reverse is the case for a positive electric field. Moreover,dO Oexhibits a close relationship with: the larger the, the longer the will be, sois elongated to about1.47under1.5V/and it is shortened by0.06under1.5V/. Since the elongation of indicates signifcant weakening of the O O bond andcontributes to a better catalytic activity, these fndings can provide a new avenue to tune theO2adsorption process onto Au-doped graphene substrate and may be useful in the futureapplications of graphene-based nanocatalyst.Our simulation data and results contribute to a better understanding of the gas moleculesinteracting with metal-doped graphene, it also provide us with some useful guidance andsuggestions for preparing metal-graphene complexes as high performance gas storagematerials, sensoring platforms, catalysts and so forth. |
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