学位プログラム名: 京都大学大学院思修館 / 京都大学 / 新制・課程博士 / 博士(総合学術) / 甲第23346号 / 総総博第19号 / 新制||総総||3(附属図書館) / 京都大学大学院総合生存学館総合生存学専攻 / (主査)教授 寶 馨, 教授 内本 喜晴, 特定教授 橋本 道雄 / 学位規則第4条第1項該当 / Doctor of Philosophy / Kyoto University / DFAM

The tip generation/substrate collection mode (TG/SC) of scanning electrochemical microscopy (SECM) was used to study the ORR reactivity on Pt catalysts in sulfuric acid solution. The SECM reactivity image and the photographic image of different single crystalline regions of the etched Pt electrode correlated well. The electron backscatter diffraction (EBSD) image of Pt confirmed the surface single crystalline orientation. The image resolution is improved by employing smaller tip-substrate distance. The kinetics of the ORR on Pt surface was also studied at -15 - 30 C by means of the rotating disk voltammetry techniques. The calculated Tafel slopes for 0.1 m and 0.9 m HClO4 changed with decreasing temperature, indicating lower kinetics at low temperature. Peroxide is produced at potentials below 0 V vs SCE.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

<p>Catalysts play an essential role in nearly every chemical production process. Platinum supported on high surface area carbon substrates (Pt/C) is one of the promising candidates as an electrocatalyst in low temperature polymer electrolyte fuel cells. Developing the activity of the Pt/C catalyst with narrow Pt particle size distribution and good dispersion has been a main concern in current research.</p> <p><br /> In this study, the main objective was the development and characterization of inexpensive and effective nanophase Pt/C electrocatalysts. A set of modified Pt/C electrocatalysts with high electrochemical activity and low loading of noble metal was prepared by the impregnation-reduction method in this research. The four home-made catalysts synthesized by different treatments conditions were characterized by several techniques such as EDS, TEM, XRD, AAS, TGA, BET and CV.</p> <p><br /> Pt electrocatalysts supported on acid treatment Vulcan XC-72 electrocatalysts were produced successfully. The results showed that Pt particle sizes of Pt/C (PrOH)x catalysts between 2.45 and 2.81nm were obtained with homogeneous dispersion, which were more uniform than the commercial Pt/C (JM) catalyst. In the electrochemical activity tests, ORR was confirmed as a structure-sensitive reaction. The Pt/C (PrOH/pH2.5) showed promising results during chemically-active surface area investigation, which compared well with that of the commercial standard Johnson Matthey Pt/C catalyst. The active surface area of Pt/C (PrOH/pH2.5) at 17.98m2/g, was higher than that of the commercial catalyst (17.22 m2/g ) under the conditions applied. In a CV electrochemical activity test of Pt/C catalysts using a Fe2+/Fe3+ mediator system study, Pt/C (PrOH/pH2.5) (67mA/cm2) also showed promise as a catalyst as the current density is comparable to that of the commercial Pt/C (JM) (62mA/cm2).</p> <p><br /> A remarkable achievement was attained in this study: the electrocatalyst Pt supported on CNTs was synthesized effectively. This method resulted in the smallest Pt particle size 2.15nm. In the electrochemically-active surface area study, the Pt/CNT exhibited a significantly greater active surface area (27.03 m2/g) and higher current density (100 mA/cm2) in the Fe2+/Fe3+ electrochemical mediator system than the other home-made Pt/C catalysts, as well as being significantly higher than the commercial Pt/C (JM) catalysts. Pt/CNT catalyst produced the best electrochemical activities in both H2SO4 and K4[Fe(CN)6] electrolytes. As a result of the characteristics of Pt/CNT，it can be deduced that the Pt/CNT is the best electrocatalyst prepared in this study and has great potential for use in fuel cell applications.</p>