SYNTHESES OF NANO-STRUCTURED GRAPHITE INTERCALATION COMPOUNDS AS A ELECTRO- AND A PHOTO- CATALYSTS AND THEIR APPLICATION TO THE PHOTOCATALYTIC HYDROGEN PRODUCTION AND THE ELCTROCATALYTIC REDUCTION OF CARBON DIOXIDE

主要研究结果如下：(1)研究发现，纳米结构的石墨层间化合物(GICs)在水溶液中可以被氙光敏化。本工作研究了GICs的光电化学特性，并对其光敏化机理进行了探讨。(2)CuCl2-GICs悬浮液中加入金属铜粉后，在甲醇水溶液中产生氢气。研究了光照时间、甲醇浓度和CuCl2-GICs含量对光催化产氢的影响。(3)在循环伏安测试中，CuCl2-GICs的电化学行为与铜电极在饱和二氧化碳的碳酸氢钾溶液中的电化学行为相似。根据相似性，我们可以预期CuCl2-GICs在二氧化碳的电化学还原中具有电催化性能，因为在文献中铜电极因其还原而被公认为电催化剂。因此，在饱和二氧化碳的碳酸氢钾水溶液中，研究了二氧化碳的电催化还原。生成的气态产物是二氧化碳还原产生的一氧化碳和甲烷，以及水分解产生的氢气。(4)提出了牺牲硫-石墨电极的新用途。综上所述，从较低的阴极过电位和较高的产物收率的角度来看，S-C电极对芳香胺的N-甲苯基化反应是有效的。

The results of this research are summarized as follows.(1)It was found that nano-structured graphite intercalation compounds (GICs) with copper chloride were sensitized by the photoillumination of xenon light in an aqueous solution. In the present work, the photoelectrochemical characteristics of the GICs were investigated and also the mechanism for the photosensitization was discussed.(2)The photoillumination to a suspension of CuCl_2-GICs with a metallic copper powder resulted in a hydrogen production in an aqueous methanol solution. The mechanistic approach was performed by considering the dependences of illumination time, methanol concentration, and content of CuCl_2-GICs to the photocatalytic hydrogen production.(3)On cyclic voltammograms measured, CuCl_2-GICs revealed similar electrochemical behavior to that of copper electrode in an aqueous potassium bicarbonate solution saturated with carbon dioxide. From the similarity we could expect the electrocatalytic property of CuCl_2-GICs in the electrochemical reduction of carbon dioxide, because copper electrode has been well known as an electrocatalyst for its reduction in the literature. Thus electrocatalytic reduction of carbon dioxide was investigated in an aqueous potassium bicarbonate solution saturated with carbon dioxide. The resulting gaseous products are carbon monoxide and methane from the reduction of carbon dioxide, in addition to hydrogen from a water decomposition.(4)We proposed the new use of the sacrificial sulfur-graphite electrode. In conclusion, the S-C electrode was found to be useful for N-tolylation of aromatic amines from the standpoint of lower cathodic overpotential and higher product yields.