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

本研究的目的是通过实验的方法来理解和讨论基于各种纳米尺度的离子或离子电子混合氧化物材料组成的异质界面的电子结构、电化学性质和离子输运性质之间的关系，从而确定纳米空间设计的方向，以实现异质界面的新功能。在对最初的实验计划稍作改动的情况下，各种氧化物和硫化物体系的电化学性质在电子能带结构的关联中得到了广泛的研究。整个研究的成果总结如下：1.利用各种电子能谱测量手段，研究了能带弯曲行为，认为能带弯曲行为是由相应能级的性质和态密度(DOS)决定的。对于具有d电子和f电子的氧化物，从O2p到MMD/nf的电荷转移反应控制着表面能级，可能还控制着界面能级。D2.提出了一种新的非化学计量比诱导载流子修饰的概念，用于封闭可逆电极的非对称电池。实验观察到阻断电极区附近电导率的变化，并将其归因于直流I-V特性的反肖特基整流。将这一概念推广到氧化物体系，并进行了实验验证，得出结论：该概念适用于具有一定离子转移数的化合物。用从头算分子动力学方法模拟了金属氧化物、质子导体和气相三相区界面的动态结构和电子驰豫以及氢和水的表面反应性的改变。

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.