Basic research for the development of coupled reactivity of electrons and ions by nano-space design of oxide hetero-composites

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The objectives of the present study is to pursue an experimental approach to understand and discuss the correlation between electronic structure, electrochemical and ionic transport properties of heterogeneous interface composed of either ionic or mixed ionic-and-electronic oxide materials fabricated based on various nano-scaled designs, in order to establish the directions of nano-space design to realize novel functionality of heterogeneous interface. With small alteration of the initial experimental plan, various oxides and sulfide systems have been extensively examined for its electrochemical properties in correlation of electronic band structure. The achievement throughout whole term is summarized as follows:1. Using various electron spectroscopy measurements, the band bending behavior has been examined and concluded that the band cramp behavior is determined by the nature and density of state (DOS) of the corresponding level. In case of oxide with d-and f-electrons, the charge transfer reaction from O2p to Mmd/nf govern the surface level and possibly the interfacial one. d2. A novel concept of Nonstoichiometry-Induced Carrier Modification has been proposed for the asymmetric cell with blocking and reversible electrode. The change in the conductivity in the vicinity of blocking electrode region is experimentally observed and is attributed for the anti-Schottky type rectification in dc I-V properties. The concept is extended to oxide systems with the experimental confirmations and is concluded to be applicable to compounds with a certain level of ionic transference number.3. A dynamic structural and electronic relaxation of interface and resultant modification of surface reactivity of hydrogen and water at the tri-phase region of metal oxide, proton conductor, and gas phase are simulated using ab-initio molecular dynamics technique.