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In the past decade, quantum-mechanical calculations have increasingly contributed in materials science studies, not only in the fundamental understanding of atomistic phenomena but also in drawing frameworks and design principles/guidelines for future technologies. In the same way, experimental techniques have advanced with the introduction of novel capabilities to build, see and manipulate materials at the atomic scale. Given these circumstances, there is a continuing high demand in developing theoretical methods and techniques that could efficiently and accurately confirm, predict, explain phenomena and introduce structures with novel properties, capable of synthesis. In this presentation, we focus on the first principles-based COMPUTATIONAL MATERIALS DESIGN (CMDŽ) [1] which encompasses various computational techniques to aid in the understanding phenomena and in the design of desired materials for exhaust gas conversion. Very briefly, the exhaust gas conversion is studied in relation to addressing strict emission standards for today's engines. Diesel Oxidation Catalyst (DOC) has been widely investigated to limit emission of harmful gases such as NOx, CO, Hydrocarbon (HC). One major obstacle of this research however is the necessity for noble metals as catalysts. Thus, interests have been laid on metal nano-particles and metal oxide support, which are candidates for lesser precious metal-loading and offer promise for tuned catalytic activity. In line with experimental studies, our computational materials design approach takes an important role in this DOC development. Here, we will show several computational works on the noble metal nano-particles on metal/metal oxide surfaces such as Pt on Al2O3 (alumina) [2] and Pt on CeO2 (ceria). Reaction pathways for HC conversion to CO2 and H2O focusing on the role of the oxidation of the catalysts will be clarified in these systems. Because of the importance of the oxidation process in DOC, we likewise tackle several case studies of theoretical approaches employing first-principles density functional theory on the oxidation of various metals (Pt-alloys) [3-5] and polymers (porphyrin, pyrrole) [6,7]. Details of these approaches and results will be discussed in the meeting. References: [1] H. Kasai et al., Introduction to Computational Materials Design - From the Basic to Actual Applications, Osaka University Press (2005) [2] F. Oemry, M. C. S. Escano, H. Kishi, S. Kunikata, H. Nakanishi, H. Kasai, H. Meakawa, K. Osumi, Y. Tashiro, J. Nanosci. Nanotech. 11 (2011) 2844 [3] W. T. Cahyanto, F. Oemry, A. A. B. Padama, M. Sakaue, R. Belkada, S. M. Aspera, M. Chikaishi, S. Kunikata, H. Nakanishi, H. Kasai, H. Maekawa, K. Osumi, Y. Tashiro, Jpn. J. App. Phys. (accepted) [4] M. C. S. Escano, H. Nakanishi, H. Kasai, J. Phys. Chem. A 113 (2009) 14302 [5] M. C. S. Escano, T. Q. Nguyen, H. Nakanishi, H. Kasai, Surf. Sci. 602 (2008) 3415 [6] T. Q. Nguyen, M. C. S. Escano, N. Shimoji, H. Nakanishi, H. Kasai, Phys. Rev. B 77 (2008) 195307 [7] H. K. Dipojono, A. G. Saputro, R. Belkada, H. Nakanishi, H. Kasai, M. David, E. S. Dy, J. Phys. Soc. Jpn. 78 (2009) 094710 |
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