Photoelectrochemical Reduction of CD_2 using Diamond Electrode

在当前的社会形势下，全球变暖等环境问题是非常严重的问题，而废气二氧化碳的回收利用是非常紧迫的挑战。我们正在尝试将电化学方法应用于二氧化碳的回收利用。我们最关注的是利用金刚石电极进行光电化学还原，并正在开发一套完整的系统，可以制造有用的产品，如乙烯或酒精。由于金刚石的物理硬度或高导热性，一直被用作切割工具或散热片。目前，金刚石凭借其半导体特性和高导热性能被认为是下一代电子器件。另一方面，在本研究中，我们利用了金刚石的半导体行为和化学稳定性，这是我们独创的想法。由于这种化学稳定性，我们在任何情况下都不需要关心电极的劣化。在这项研究中，金刚石电极在连续电解几天后实际上非常稳定。1)用微波等离子体化学气相沉积法制备了p型金刚石半导体自支撑薄膜电极，并对其性能进行了测试。2)比较了自支撑金刚石电极和金刚石电极与硅衬底在Xe-Hg灯下的光电化学行为。3)比较了金刚石薄膜电极与其他电化学、光电化学和光催化方法对CO_2的光电化学还原效果。4)研究了高效率、高电流密度的金刚石电极光电化学还原的最佳条件。5)研究了电极、电解液、6)考察了金刚石电极在恶劣条件下的应用情况，并考察了该电极在长期电解条件下的稳定性。

Environmental problems such as global warming are very serious problems under the recent social situation and recycling of the exhausted carbon dioxide is the very urgent challenge. We are attempting to apply electrochemical methods to the recycling of carbon dioxide. We pay most attention to photoelectrochemical reduction using Diamond electrodes, and are developing a whole system which can make the useful products, such as ethylene or alcohol. Diamond has been using as cutting implement or heat sink due to its physical hardness or high heat conductivity. Now diamond is considered as a next-generation electronic device by the use of semiconducting behavior and high heat conductivity. On the other hand, we make use of semiconducting behavior and chemical stability of the diamond in this study, and this idea is our original and unique one. Due to this chemical stability, we need not care about deterioration of the electrodes under any conditions. In this study, diamond electrodes are actually very stable under continuous electrolysis for several days. The following lists the yearly results in this study.1) We made free-standing thin film electrodes of p-type diamond semiconductor with the microwave plasma CVD, and examined the behavior.2) We compared the photoelectrochemical behavior of free-standing diamond electrodes and diamond electrodes with silicon substrate under Xe-Hg lamp illumination.3) We compared the photoelectrochemical CO_2 reduction using diamond thin film electrodes and other electrochemical, photoelectrochemical or photocatalytic method.4) We examined the optimum conditions for the photoelectrochemical reduction using diamond electrode with high efficiency and high current density.5) We examined the optimum conditions for preparation of the electrode, electrolyte, and so on.6) We examined the application of diamond electrode under severe conditions and examined the stability of the electrode under long-term electrolysis.