1. Density Functional Theory Studies of Dehydrogenation of Methane and Hydrogenation of
Benzene over Ni-and Ru-based Bimetallic Catalyst-Medical Journal
The reactions involving breaking and making of a C-H bond on transition metal surfaces is one of
the hottest research points in heterogeneous catalysis. The addition of another metal as a promoter
can improve the efficiency of this process. In the thesis, first-principle calculations based on
density functional theory are used to investigate the reaction mechanism for hydrogenation and
dehydrogenation reactions on metal surfaces, where the activation of methane on Ni catalyst and
hydrogenation of benzene on Ru catalyst are taken as the research systems. By examining the
effect of the metal promoters in the catalysts, the synergetic effects of the bimetallic catalysts as
well as the C-H bond breaking and making mechanism are revealed. The main results of the work
are summarized as follows:(1) The dry reforming of methane on Ni catalyst is investigated. The
adsorption energies of all the reaction intermediates as well as the activation energies for all the
elementary reactions that involved in dry reforming of methane on Ni(111), Ni(100) and Ni(211)
surfaces are calculated. With the combination of the DFT results and statistic thermodynamic
formulism as well as the transition state theory, the reaction constants for all the elementary
reactions are estimated. Based on this, a full microkinetic model is constructed, and the surface
coverages of the reaction intermediates and the reaction rates for all the elementary reactions are
obtained. Thus, the dominant reaction pathway and the rate-determining step are identified.(2) The
activation of methane on alloyed Ni/Fe(111) surface is investigated. Two bulk models with
different Ni to Fe molar ratios are constructed and XRD simulations are conducted to evaluate
their reliability. The calculated results show that, with the increase of the Fe content, the
adsorption of the reaction intermediates involved in methane dissociation is strengthened, which
facilitates the formation of surface C atoms. The dissolution of C from surface to the bulk of the
catalyst particle is found to be thermodynamically favorable, and the diffusion of C through the
catalyst particle is hindered as the Fe content increases. With the combination of the kinetic
analysis, the effect of the reaction conditions on the C concentration in the catalyst particle is
revealed.(3) The synergetic effects of Ni-based bimetallic catalyst are investigated. Several
transition metals are introduced into the Ni catalyst, and the surface alloy models are constructed
accordingly. The activation of methane is taken as a probe reaction to investigate the synergetic
effect. The ensemble effect and the ligand effect of the bimetallic catalyst are discussed, and the
electrostatic interaction energy between Ni atom and the second metal atom are estimated. Using
the activation energy of the first step in methane dissociation and the C binding energy as
descriptors, the optimal catalyst for activation of methane is single out. which gives some insights
into rational designing new catalyst.(4) The reaction mechanism for benzene hydrogenation on
Ru(0001) surface is investigated. The adsorption energies of all the possible reaction intermediates
are calculated, and the most stable adsorption configurations as well as the most stable isomers on
Ru(0001) are identified. Based on this, the activation energies for the six elementary reactions in
hydrogenation of benzene to cyclohexane are calculated in both low and high H coverages, and
the high H coverage is found to be very crucial for the reaction. Theπ-mode adsorption is a key
point to produce cyclohexene on Ru catalyst.(5) The effect of the introduction of Zn into Ru
catalyst on the selectivity to cyclohexene is investigated. The adsorption energies of the reaction
intermediates and the activation energies for the elementary reactions are calculated. With the
comparison to the results from the conditions at different H coverages, the effect of Zn on the

2. selectivity to cyclohexene is revealed. Zn is found to facilitate the desorption and retard the deep
hydrogenation of cyclohexene, which leads to the incease of the selectivity to cyclohexene.
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