Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Yasuda, Satoshi; Uchibori, Yosuke*; Wakeshima, Makoto*; Hinatsu, Yukio*; Ogawa, Hiroaki; Yano, Masahiro; Asaoka, Hidehito
RSC Advances (Internet), 8(66), p.37600 - 37605, 2018/11
Times Cited Count：12 Percentile：42.2(Chemistry, Multidisciplinary)We present a quantitative study on the effect of a newly obtained thermal history on the formation of Fe-N-C catalytic sites. A short and repeated heating process is employed as the new thermal history, where short heating (1 min) followed by quenching is applied to a sample with arbitrary repetition. Through electrochemical quantitative analysis, it is found that the new process effectively increases the Fe-N-C mass-based site density (MSD) to almost twice that achieved using a conventional continuous heating process, while the turn-over frequency (TOF) is independent of the process. Elemental analysis shows that the new process effectively suppresses the thermal desorption of Fe and N atoms during the initial formation stage and consequently contributes to an increase in the Fe-N-C site density. The resultant catalytic activity (gravimetric kinetic current density (0.8 V vs. RHE)) is 1.8 times higher than that achieved with the continuous heating process.
Ota, Tomonori*; Hagiwara, Tokio*; Sugimoto, Masaki; Yamamoto, Shunya; Koshikawa, Hiroshi; Yamaki, Tetsuya
no journal, ,
Nitrogen (N)-doped carbon-based electrocatalysts are expected as a platinum alternative material for cost reduction of polymer electrolyte membrane fuel cells. However, nobody has not yet established the method of introducing N atoms in a graphene structure at high concentrations. Therefore, our purpose is to propose a new method of N doping using electron beam irradiation at high temperatures in an ammonia atmosphere. We developed here a sample chamber with a heating device, gas inlet and outlet, which made it possible to perform the irradiation without any temperature change. As a result, the phenolic resin, that is, a source of carbon-based electrocatalysts was irradiated with 2 MeV electrons at a dose rate of 2 kGy/s while being maintained at 300 
C with a high precision as 
2 C.
Ota, Tomonori*; Yamaki, Tetsuya; Sugimoto, Masaki; Yamamoto, Shunya; Koshikawa, Hiroshi; Hagiwara, Tokio*
no journal, ,
Nitrogen-doped carbon-based catalysts are expected as Pt alternatives, and however there have been so far no established methods to introduce N atoms into graphene structures. Thus, we report N doping in carbon-based catalysts by electron beam (EB) irradiation in ammonia (NH
). A precursor was phenolic resin or its mixture with 5 or 10 wt% cobalt(II) chloride (CoCl
); it was then irradiated with 2 MeV electron beam up to a dose of 6 MGy in 1 vol% NH at 400C. This irradiated powder was carbonized in an Ar atmosphere at 800C for 1 h. An N-doping level reached an atomic concentration of ca. 0.5% when 5 wt% CoCl was mixed in the precursor.
Sugimoto, Masaki; Ota, Tomonori*; Yamamoto, Shunya; Koshikawa, Hiroshi; Yamaki, Tetsuya; Hagiwara, Tokio*
no journal, ,
no abstracts in English
