Simulation of Initial Growth Process of Pt Cluster on Carbon Materials - First-Principles Calculations
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1130-W12-25
Simulation of Initial Growth Process of Pt Cluster on Carbon Materials - First-Principles Calculations K. Okazaki-Maeda1, S. Yamakawa2, Y. Morikawa3, S. Hyodo2, T. Akita4, Y. Maeda4, S. Tanaka4, and M. Kohyama4 1Department of Mechanical Engineering, Osaka University, 2-1 Yamada-oka, Suita 565-0871, Japan. 2Toyota Central R&D Labs., Inc., Nagakute, Aichi 480-1192, Japan. 3ISIR, Osaka University, 8-1 Mihigaoka, Ibaraki 567-0047, Japan. 4UBIQEN, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda 563-8577, Japan. ABSTRACT First-principles calculations have been applied to investigate the interactions between Ptn (n=1~13) clusters and a graphene sheet to model the Pt/C fuel-cell catalytic electrode. For the small clustesr (n7), the 3D clusters are more stable than the V-2D clusters. In order to investigate the effects of defects and dopants in a graphene sheet, the interactions between the Pt13 cluster and the graphene sheet with an atomic vacancy and an dopant atom, such as boron and nitrogen atoms have been examined. For the atomic vacancy, the Pt atom is directly adsorbed on the C atom vacant site. For the Pt13 cluster adsorbed on the graphene sheet doped with the B or N atoms, the Pt atom is not directly adsorbed on the impurity atoms. The adsorption of the Pt13 cluster above the vacancy of the graphene sheet is more stable that that on the doped graphene sheet in the present calculations. INTRODUCTION Platinum (Pt) nano-particles supported on carbon materials are used as electrode catalysts for a proton exchange membrane fuel cell (PEMFC) [1]. The performance is affected by the size distribution of Pt nano-particles and the condition at the interface between Pt nano-particles and carbon materials. Therefore, it is important to investigate the growth process of Pt nano-particles on carbon materials. We previously investigated the interaction between small Ptn clusters (n=1-4) and graphene without any defects by the first-principles calculations [2]. Yamakawa et al. have also simulated the growth process of Pt nano-particles on carbon supports by the phasefield method [3], where the first-principles results were referred as the interaction energy between Pt and carbon supports. In the present study, we firstly examined the interaction energy between Ptn clusters (n=1-13) and a graphene sheet in order to enhance the simulation accuracy. It is important to stabilize the Pt nano-particles on the carbon materials in order to design the electrode catalysis. It is reported that the vacancy in the graphene sheet enhanced the interfacial interaction between the Pt atom and the graphene sheet [2, 4] and that very small clusters are more stable adsorbed on the carbon supports with substitutional boron-dopants [5].
Therefore, second in the present study, we examined the interaction energy between a 3D Pt13 cluster and graphene including atomic vacancies, in order to investigate the effects of defects. METHOD OF CALCULATIONS All the calculations were carried out using the pr
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