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成果報告書詳細
管理番号20190000000144
タイトル*2018年度中間年報 固体高分子形燃料電池利用高度化技術開発事業/普及拡大化基盤技術開発/金属原子直接担持による触媒高性能化コンセプトの提案
公開日2019/6/11
報告書年度2018 - 2018
委託先名学校法人東京理科大学
プロジェクト番号P15001
部署名次世代電池・水素部
和文要約
英文要約Abstract
Design of high-performance catalysts for PEFC by direct deposition of metal on carbon support

 Platinum (Pt) nanoparticles were deposited on a HOPG substrate using a coaxial arc plasma gun with a condenser capacity of 300 μF and a discharge voltage of 300 V for 25 times (to a Pt-loading of 2.4 μg・cm-2). A high-resolution transmission electron microscopy observation showed that graphene layers of the HOPG substrate became non-crystalline by the irradiation of Pt ions. Using electron energy-loss spectroscopy for the Pt-deposited HOPG substrate, values of full width at half maximum (FWHM) of carbon π* peaks were plotted in the depth direction. The depth profile of FWHM showed the maximum value from which the surface position of HOPG substrate was deduced. The matrix of HOPG substrate was found to be damaged to a depth of ~20 nm by the Pt ion irradiation.
 Atomic scale mechanism of APD deposition method were investigated using a first principles calculation. In this year, we have investigated the diffusion behavior of Pt on graphene and amorphous carbon. The diffusion behavior was investigated using a nudged elastic band (NEB) method. A diffusion path from the most stable site (vacancy site and bridge site for the graphene and amorphous, respectively) to surrounding sites was considered, and the number of images for the NEB calculations was set five. The migration energy in the graphene was approximately 4 eV, whereas it in the amorphous model was under 1 eV, indicating that the adsorbed Pt at the vacancy site in the graphene is hard to migrate but that on the amorphous can move to surroundings. In the graphene, the vacancy site is much more stable than other sites, namely large “gap”. The “gap” is much smaller on the amorphous carbon because there are many stable sites on the amorphous surface. We can conclude that the this “gap” can be the design guideline for the catalysis carbon.
 The adsorption properties of hydrogen on the Pt nanoparticles supported on glassy carbon (GC) substrates were analyzed with thermal desorption spectroscopy (TDS). A novel sample holder and heating technique was implemented to allow performing TDS measurements on real catalyst samples consisting of APD-deposited Pt nanoparticles (to a loading of 1.6 μg・cm-2) on commercial GC electrode disks. When the sample was exposed to molecular hydrogen, only a very weak hydrogen desorption signal was observed in TDS. When the sample was exposed to atomic hydrogen, on the other hand, a stronger hydrogen desorption signal was observed suggesting that there exists an activation barrier for dissociative adsorption of hydrogen on the Pt clusters.
 Dissolution behavior of Pt nanoparticles prepared by APD method was investigated by an inductively coupled plasma mass spectroscopy (ICP-MS) and a channel flow double electrode (CFDE) system. ICP-MS analysis revealed that the amount of dissolved Pt from Pt nanoparticles is higher than that from Pt films due to instability of Pt nanoparticles. It is also higher than that from commercial Pt/C catalysts, however stability of Pt nanoparticles made by APD needs further study because evaluation method for Pt/C using ICP-MS is not completely established. Pt dissolution from Pt nanoparticles is not detected using CFDE, because the amount of Pt loading is small and hydrogen peroxide detection might hide Pt detection. Now, we continue to detect Pt nanoparticles dissolution using this technique.
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