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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.


TG/DTA and DTG curves. (a) FePc/PhRs and (b) HB-FePc precursor.
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Fig3: TG/DTA and DTG curves. (a) FePc/PhRs and (b) HB-FePc precursor.

Mentions: TG-DTA/DTG curves of the FePc/PhRs and HB-FePc precursors are presented in Figure 3. In the case of the FePc/PhRs precursor, two large DTG mass loss peaks are observed at around 230°C and 340°C. From the mass spectrum (not shown), the molecular weight of these peaks corresponds to phenol (m/z = 94). The DTG curve of the HB-FePc precursor does not show any significant peaks, implying that the biphenyl linker is stable below 500°C. Instead, the DTG curve of the HB-FePc precursor shows two large peaks at around 600°C and 830°C. The corresponding structure also appears in the DTG curve of the FePc/PhRs precursor, but with much smaller weight loss compared with that of the HB-FePc precursor. In other words, the main decomposition region of the HB-FePc precursor appears at a higher temperature (above 600°C) than that of the FePc/PhRs precursor. This may be because in the HB-FePc catalyst, the biphenyl linker connecting phthalocyanine moieties does not decompose, which suppresses liberation/sublimation of each component below 600°C. The DTA curve of the HB-FePc precursor has exothermal peaks at 650°C and 830°C, suggesting that graphitization occurs in the same temperature range as the main decomposition of the HB-FePc precursor. In contrast, the DTA curve of the FePc/PhRs precursor shows a graphitization peak around 800°C. Taking into account both the DTA and DTG curves of the FePc/PhRs precursor, decomposition occurs gradually above 600°C, while graphitization occurs exclusively at around 800°C.Figure 3


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)

TG/DTA and DTG curves. (a) FePc/PhRs and (b) HB-FePc precursor.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig3: TG/DTA and DTG curves. (a) FePc/PhRs and (b) HB-FePc precursor.
Mentions: TG-DTA/DTG curves of the FePc/PhRs and HB-FePc precursors are presented in Figure 3. In the case of the FePc/PhRs precursor, two large DTG mass loss peaks are observed at around 230°C and 340°C. From the mass spectrum (not shown), the molecular weight of these peaks corresponds to phenol (m/z = 94). The DTG curve of the HB-FePc precursor does not show any significant peaks, implying that the biphenyl linker is stable below 500°C. Instead, the DTG curve of the HB-FePc precursor shows two large peaks at around 600°C and 830°C. The corresponding structure also appears in the DTG curve of the FePc/PhRs precursor, but with much smaller weight loss compared with that of the HB-FePc precursor. In other words, the main decomposition region of the HB-FePc precursor appears at a higher temperature (above 600°C) than that of the FePc/PhRs precursor. This may be because in the HB-FePc catalyst, the biphenyl linker connecting phthalocyanine moieties does not decompose, which suppresses liberation/sublimation of each component below 600°C. The DTA curve of the HB-FePc precursor has exothermal peaks at 650°C and 830°C, suggesting that graphitization occurs in the same temperature range as the main decomposition of the HB-FePc precursor. In contrast, the DTA curve of the FePc/PhRs precursor shows a graphitization peak around 800°C. Taking into account both the DTA and DTG curves of the FePc/PhRs precursor, decomposition occurs gradually above 600°C, while graphitization occurs exclusively at around 800°C.Figure 3

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.