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Active site formation mechanism of carbon-based oxygen reduction catalysts derived from a hyperbranched iron phthalocyanine polymer.

Hiraike Y, Saito M, Niwa H, Kobayashi M, Harada Y, Oshima M, Kim J, Nabae Y, Kakimoto MA - Nanoscale Res Lett (2015)

Bottom Line: The properties of the HB-FePc catalyst are compared with those of a catalyst with high oxygen reduction reaction (ORR) activity synthesized from a mixture of iron phthalocyanine and phenolic resin (FePc/PhRs).Electrochemical measurements demonstrate that the HB-FePc catalyst does not lose its ORR activity up to 900°C, whereas that of the FePc/PhRs catalyst decreases above 700°C.Consequently, effective doping of active nitrogen species into the sp (2) carbon network of the HB-FePc catalysts may occur up to 900°C.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656 Japan ; Current address: Toray Industries, Incorporated, Nihonbashi-Muromachi 2-chome, Tokyo, Japan.

ABSTRACT
Carbon-based cathode catalysts derived from a hyperbranched iron phthalocyanine polymer (HB-FePc) were characterized, and their active-site formation mechanism was studied by synchrotron-based spectroscopy. The properties of the HB-FePc catalyst are compared with those of a catalyst with high oxygen reduction reaction (ORR) activity synthesized from a mixture of iron phthalocyanine and phenolic resin (FePc/PhRs). Electrochemical measurements demonstrate that the HB-FePc catalyst does not lose its ORR activity up to 900°C, whereas that of the FePc/PhRs catalyst decreases above 700°C. Hard X-ray photoemission spectra reveal that the HB-FePc catalysts retain more nitrogen components than the FePc/PhRs catalysts between pyrolysis temperatures of 600°C and 800°C. This is because the linked structure of the HB-FePc precursor has high thermostability against nitrogen desorption. Consequently, effective doping of active nitrogen species into the sp (2) carbon network of the HB-FePc catalysts may occur up to 900°C.

No MeSH data available.


Electrochemical characterization of the catalysts. Linear sweep voltammograms of (a) FePh/PhRs and (b) HB-FePc catalysts and onset potential and current density plots as a function of pyrolysis temperature (bottom) of (c) FePc/PhRs and (d) HB-FePc catalysts.
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Fig2: Electrochemical characterization of the catalysts. Linear sweep voltammograms of (a) FePh/PhRs and (b) HB-FePc catalysts and onset potential and current density plots as a function of pyrolysis temperature (bottom) of (c) FePc/PhRs and (d) HB-FePc catalysts.

Mentions: Figure 2 shows linear sweep voltammograms of (a) the FePc/PhRs and (b) HB-FePc carbon-based cathode catalysts (hereafter denoted simply as FePc/PhRs and HB-FePc catalysts) measured by the RDE method. The corresponding onset potential and current density as a function of pyrolysis temperature for the FePc/PhRs and the HB-FePc catalysts are plotted in Figure 2c,d. Among the FePc/PhRs catalysts, Fe600 shows the highest onset potential (0.92 V) with the largest current density at 0.5 V. For pyrolysis temperatures above 600°C, the onset potential decreases slightly and the current density at 0.5 V degrades markedly. In contrast, the ORR activity of the HB-FePc catalysts increases at a pyrolysis temperature of around 650°C (onset potential = 0.87 V for HB650) and remains almost unchanged up to 900°C (0.89 V for HB900). It is remarkable that the ORR activity of the HB-FePc catalysts is retained at such high pyrolysis temperatures compared with that of the FePc/PhRs catalysts. Specific BET surface areas of both samples are summarized in Table 1. The values are between 337 to 564 m2 g−1, suggesting that the pore structures of these samples do not have significant impacts on the ORR activity.Figure 2


Active site formation mechanism of carbon-based oxygen reduction catalysts derived from a hyperbranched iron phthalocyanine polymer.

Hiraike Y, Saito M, Niwa H, Kobayashi M, Harada Y, Oshima M, Kim J, Nabae Y, Kakimoto MA - Nanoscale Res Lett (2015)

Electrochemical characterization of the catalysts. Linear sweep voltammograms of (a) FePh/PhRs and (b) HB-FePc catalysts and onset potential and current density plots as a function of pyrolysis temperature (bottom) of (c) FePc/PhRs and (d) HB-FePc catalysts.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401482&req=5

Fig2: Electrochemical characterization of the catalysts. Linear sweep voltammograms of (a) FePh/PhRs and (b) HB-FePc catalysts and onset potential and current density plots as a function of pyrolysis temperature (bottom) of (c) FePc/PhRs and (d) HB-FePc catalysts.
Mentions: Figure 2 shows linear sweep voltammograms of (a) the FePc/PhRs and (b) HB-FePc carbon-based cathode catalysts (hereafter denoted simply as FePc/PhRs and HB-FePc catalysts) measured by the RDE method. The corresponding onset potential and current density as a function of pyrolysis temperature for the FePc/PhRs and the HB-FePc catalysts are plotted in Figure 2c,d. Among the FePc/PhRs catalysts, Fe600 shows the highest onset potential (0.92 V) with the largest current density at 0.5 V. For pyrolysis temperatures above 600°C, the onset potential decreases slightly and the current density at 0.5 V degrades markedly. In contrast, the ORR activity of the HB-FePc catalysts increases at a pyrolysis temperature of around 650°C (onset potential = 0.87 V for HB650) and remains almost unchanged up to 900°C (0.89 V for HB900). It is remarkable that the ORR activity of the HB-FePc catalysts is retained at such high pyrolysis temperatures compared with that of the FePc/PhRs catalysts. Specific BET surface areas of both samples are summarized in Table 1. The values are between 337 to 564 m2 g−1, suggesting that the pore structures of these samples do not have significant impacts on the ORR activity.Figure 2

Bottom Line: The properties of the HB-FePc catalyst are compared with those of a catalyst with high oxygen reduction reaction (ORR) activity synthesized from a mixture of iron phthalocyanine and phenolic resin (FePc/PhRs).Electrochemical measurements demonstrate that the HB-FePc catalyst does not lose its ORR activity up to 900°C, whereas that of the FePc/PhRs catalyst decreases above 700°C.Consequently, effective doping of active nitrogen species into the sp (2) carbon network of the HB-FePc catalysts may occur up to 900°C.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656 Japan ; Current address: Toray Industries, Incorporated, Nihonbashi-Muromachi 2-chome, Tokyo, Japan.

ABSTRACT
Carbon-based cathode catalysts derived from a hyperbranched iron phthalocyanine polymer (HB-FePc) were characterized, and their active-site formation mechanism was studied by synchrotron-based spectroscopy. The properties of the HB-FePc catalyst are compared with those of a catalyst with high oxygen reduction reaction (ORR) activity synthesized from a mixture of iron phthalocyanine and phenolic resin (FePc/PhRs). Electrochemical measurements demonstrate that the HB-FePc catalyst does not lose its ORR activity up to 900°C, whereas that of the FePc/PhRs catalyst decreases above 700°C. Hard X-ray photoemission spectra reveal that the HB-FePc catalysts retain more nitrogen components than the FePc/PhRs catalysts between pyrolysis temperatures of 600°C and 800°C. This is because the linked structure of the HB-FePc precursor has high thermostability against nitrogen desorption. Consequently, effective doping of active nitrogen species into the sp (2) carbon network of the HB-FePc catalysts may occur up to 900°C.

No MeSH data available.