Photoelectrochemical Reduction of CD_2 using Diamond Electrode

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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.