1C17Interface effects on H2 adsorption and dissociation on gold clusters
supported on the rutile TiO2(110) surface(Kyoto University*, Hokkaido University**)○Andrey Lyalin ，Min Gao ,***

Satoshi Maeda*,**, Tetsuya Taketsugu*,**Gold nanoparticles demonstrate their great potential as an effective catalyst for hydrogenation
reactions. However, mechanisms of such catalytic reactions are largely not understood. In thepresent work we focus on the elucidation of mechanisms of H2 activation and dissociation on
the small free and supported gold clusters. It is demonstrated that adsorption of H2 on goldclusters depends on cluster size, geometry structure, cluster flexibility and interaction withthe support. In particular the role of the rutile TiO2(110) surface in the processes of H2adsorption and dissociation on the supported gold clusters is discussed.
We introduce a global reaction route mapping (GRRM) approach to find chemicalbond activation pathways catalyzed by small free gold clusters Aun (n=1–11) with the use ofanharmonic downward distortion following (ADDF) and artificial force induced reaction(AFIR) methods [1-3]. The calculations have been performed as follows: (1) automatedsearch for isomers of free gold clusters by ADDF method; (2) physical and chemical
adsorption of H2 on the obtained gold clusters by AIFR method; (3) refining the obtained
AFIR paths to find transition states (TSs) for H-H bond dissociation. All calculations arecarried out using density-functional theory (DFT) with the PBE gradient-corrected exchange–correlation functional [4]. The results of our calculations demonstrate that H2 molecule
prefers to bind to the low-coordinated gold atoms on the most stable cluster isomer. However,in that case the barrier for H2 dissociation can be relatively high. On the other hand in GRRM
approach both the global minimum (GM) and several local minima (LM) are consideredsimultaneously on the basis of ADDF and AFIR methods. Such approach allows one toreduce considerably the barriers for H2 dissociation, as it is shown in Figure 1.
160
Activiation energy (kJ/mol)

H2 Binding Energy (kJ/mol)

60

4530

150Kang et al, JCP 130, 024701 (2009) (PW91/def2-TZVPP)
traditional strategy (PBE/DZP)
favorable path, GRRM (PBE/DZP)

140120100806040
200-20012345n6789 10 11123456789 10 11nFigure 1. Binding energy of H2 adsorbed on Aun clusters as a function of cluster size (left);
activation energy for H2 dissociation obtained with the use of the traditional strategy(triangles) and GRRM approach (dots) as a function of cluster size (right).

It is well known that the support material can play an important role in the catalytic
processes, considerably influencing the chemical reactivity of the supported clusters [5]. Thus,
recently it was demonstrated experimentally that the perimeter interface between the cluster
and the support material can play the role of active sites for hydrogen dissociation by gold
nanoparticles on TiO2 support [6]. Therefore we have performed theoretical calculations ofadsorption and dissociation of H2 molecule on the gold clusters supported on the rutileTiO2(110) surface [7]. We have demonstrated that TiO2 (110) support considerably affects
geometry structure of the supported gold clusters and promotes adsorption and dissociation ofH2 on Aun/TiO2. In particular, formation of the OH group near the supported gold cluster is
an important condition for H2 dissociation, as it is shown in Figure 2. The active sites for H2
dissociation are located in the vicinity of the low coordinated oxygen atoms on the rutileTiO2(110) surface [7]. This, combination (interplay) of several factors such as geometry
structure, cluster dimensionality, presence of the low coordinated oxygen atoms in thevicinity of the cluster-surface interface, etc. are important for H2 dissociation.
Figure 2. Optimized geometries in thecase of (a) molecular adsorption of H2 on
Au8(2D)/TiO2, Eb = 23 kJ/mol;
dissociative adsorption of H2 on
Au2(2D)/TiO2: (b) dissociation of H2 on
supported Au2(2D), Eb = 72 kJ/mol; (c)dissociation of H2 with formation of theOH group on O(2) bridge atom, Eb = 150
kJ/mol. Optimized geometries in the caseof (d) molecular adsorption of H2 on
Au8(3D)/TiO2, Eb = 9 kJ/mol; dissociativeadsorption of H2 on Au2(3D)/TiO2: (e)dissociation of H2 on supported Au2(3D),
Eb = 53 kJ/mol; (f) dissociation of H2 withformation of the OH group on O(2)bridge atom, Eb = 92 kJ/mol.

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[3] S. Maeda, K. Ohno, and K. Morokuma, Phys. Chem. Chem. Phys. 15, 3683 (2013).
[4] J. P. Perdew, K. Burke and M. Ernzerhof, Phys. Rev. Lett., 77, 3865 (1996).
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[6] T. Fujitani, I. Nakamura, T. Akita, M. Okumura, and M. Haruta Angew. Chem. Int. Ed. 48,9515 (2009).
[7] A. Lyalin and T. Taketsugu, Faraday Discuss. 152, 185 (2011).