Photoelectrochemical Reduction of CD_2 using Diamond Electrode

在当前的社会形势下，诸如全球变暖的环境问题是非常严重的问题，并且回收所排放的二氧化碳是非常紧迫的挑战。我们正试图将电化学方法应用于二氧化碳的再循环。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，以生产有用的产品，如乙烯或酒精。金刚石由于其物理硬度和高导热性，一直被用作切削工具或散热器。金刚石由于具有半导体特性和高导热性，被认为是下一代电子器件。另一方面，我们利用金刚石的半导体特性和化学稳定性来进行研究，这是我们独创性的想法。由于这种化学稳定性，我们不需要关心电极在任何条件下的劣化。在这项研究中，金刚石电极实际上在连续电解数天后非常稳定。以下是本研究的年度成果：1）我们用微波等离子体CVD法制备了p型金刚石半导体自支撑薄膜电极，2）在Xe-Hg灯照射下比较了金刚石自支撑电极和硅衬底金刚石电极的光电化学行为; 3）比较了金刚石自支撑电极和硅衬底金刚石电极的光电化学行为; 4）比较了金刚石自支撑电极和硅衬底金刚石电极的光电化学行为。2、采用金刚石薄膜电极和其他电化学、光电化学或光催化方法进行还原。4）我们考察了采用高效率和高电流密度的金刚石电极进行光电化学还原的最佳条件。5）我们考察了电极、电解质、6）考察了金刚石电极在苛刻条件下的应用，考察了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.