Kazuyuki Okazaki

First-Principles Calculations of Metal/Oxide Interfaces: Effects of Interface Stoichiometry

Ab initio pseudopotential calculations of Cu/Al2O3 and Au/TiO2 interfaces have revealed strong effects of interface stoichiometry. About the Cu/Al2O3 system used for coatings and electronic devices, the interfacial bond of the O-terminated (O-rich) Cu/Al2O3(0001) interface is very strong with ionic and covalent Cu-O interactions, although that of the Al-terminated (stoichiometric) one is rather weak with electrostatic and Cu-Al hybridization interactions. About the Au/TiO2 system with unique catalytic activity, the adhesive energy between non-stoichiometric (Ti-rich or O-rich) TiO2(110) surface and a Au layer is very large, and there occur substantial charge transfer and orbital hybridization, which should have close relations to the catalytic activity.

Nanoscale characterization of Pd/TiO2 catalysts and Ag/TiO2 catalysts by electron holography

Catalytic properties of noble metal catalysts are often caused by their nanostructures and the interaction between nano particles and oxides supports. We examine the mean inner potential of Pd particles in Pd/TiO 2 catalyst and Ag particles in Ag/TiO 2 catalysts using electron holography and HRTEM. And we compare the results of the Pd/TiO 2 and Ag/TiO 2 systems with our previous results of the Au/TiO 2 and Pt/TiO 2 systems. In the case of the Pd/TiO 2 catalysts, when the size of Pd particle is smaller than 5nm, the mean inner potential of Pd changes to be higher than the calculated value of the mean inner potential which is thought to be higher than the experimental values of bulk Pd by 3-5V. The mean inner potential of Pd becomes to increase gradually as the size of the Pd particle decreases. The rate of the increment in the mean inner potential of Pd is lower than that of Au/TiO 2 catalysts and Pt/TiO 2 catalysts. On the other hand, in the case of Ag/TiO 2 catalysts, the mean inner potential of Ag does not increase though the size of the Ag particle decreases to under 2nm.