Pyrolyzed phthalocyanines as surrogate carbon catalysts

Initial insights into oxygen-transfer mechanisms

Fernando Vallejos-Burgos, Shigenori Utsumi, Yoshiyuki Hattori, Ximena García, Alfredo L. Gordon, Hirofumi Kanoh, Katsumi Kaneko, Ljubisa R. Radovic

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Deposited and heat-treated phthalocyanines are promising electrocatalysts for replacing platinum in the oxygen reduction reaction (ORR), the most important process in energy conversion systems such as fuel cells; and yet its key mechanistic features are not well understood. To optimize their use, it is necessary to understand their behavior in the absence of an electric field. In the pursuit of this goal, we pyrolyzed metal-free, cobalt and copper phthalocyanines between 550 and 1000 °C and studied their structural and chemical changes by elemental analysis, N 2 and CO 2 adsorption, X-ray diffraction (XRD), Raman spectroscopy, X-ray analysis fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). Their catalytic activity was assessed by non-isothermal O 2 gasification and NO reduction reactions. A comparison of these results with their other properties allowed us to reach the following conclusions: (i) the loss of reactivity of metal-free phthalocyanine with heat treatment is attributed to its structural annealing and heteroatom loss, with the porosity changes having no effect; (ii) for metal phthalocyanines at intermediate heat treatment temperatures, the optimum in reactivity correlates with the micropore surface area and the presence of metal particles, with no influence of nitrogen content; (iii) the coordination metal increases phthalocyanine thermal stability in an inert atmosphere, but in an oxidizing atmosphere it acts as a gasification catalyst even below decomposition temperatures. The implications of these findings for catalytic oxygen-transfer mechanisms are discussed.

Original languageEnglish (US)
Pages (from-to)106-117
Number of pages12
JournalFuel
Volume99
DOIs
StatePublished - Sep 1 2012

Fingerprint

Carbon
Metals
Oxygen
Catalysts
Gasification
Heat treatment
Electrocatalysts
X ray analysis
Carbon Monoxide
Platinum
Energy conversion
Raman spectroscopy
Fuel cells
Cobalt
Catalyst activity
Thermodynamic stability
Nitrogen
X ray photoelectron spectroscopy
Porosity
Electric fields

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Organic Chemistry

Cite this

Vallejos-Burgos, Fernando ; Utsumi, Shigenori ; Hattori, Yoshiyuki ; García, Ximena ; Gordon, Alfredo L. ; Kanoh, Hirofumi ; Kaneko, Katsumi ; Radovic, Ljubisa R. / Pyrolyzed phthalocyanines as surrogate carbon catalysts : Initial insights into oxygen-transfer mechanisms. In: Fuel. 2012 ; Vol. 99. pp. 106-117.
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abstract = "Deposited and heat-treated phthalocyanines are promising electrocatalysts for replacing platinum in the oxygen reduction reaction (ORR), the most important process in energy conversion systems such as fuel cells; and yet its key mechanistic features are not well understood. To optimize their use, it is necessary to understand their behavior in the absence of an electric field. In the pursuit of this goal, we pyrolyzed metal-free, cobalt and copper phthalocyanines between 550 and 1000 °C and studied their structural and chemical changes by elemental analysis, N 2 and CO 2 adsorption, X-ray diffraction (XRD), Raman spectroscopy, X-ray analysis fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). Their catalytic activity was assessed by non-isothermal O 2 gasification and NO reduction reactions. A comparison of these results with their other properties allowed us to reach the following conclusions: (i) the loss of reactivity of metal-free phthalocyanine with heat treatment is attributed to its structural annealing and heteroatom loss, with the porosity changes having no effect; (ii) for metal phthalocyanines at intermediate heat treatment temperatures, the optimum in reactivity correlates with the micropore surface area and the presence of metal particles, with no influence of nitrogen content; (iii) the coordination metal increases phthalocyanine thermal stability in an inert atmosphere, but in an oxidizing atmosphere it acts as a gasification catalyst even below decomposition temperatures. The implications of these findings for catalytic oxygen-transfer mechanisms are discussed.",
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Vallejos-Burgos, F, Utsumi, S, Hattori, Y, García, X, Gordon, AL, Kanoh, H, Kaneko, K & Radovic, LR 2012, 'Pyrolyzed phthalocyanines as surrogate carbon catalysts: Initial insights into oxygen-transfer mechanisms', Fuel, vol. 99, pp. 106-117. https://doi.org/10.1016/j.fuel.2012.03.055

Pyrolyzed phthalocyanines as surrogate carbon catalysts : Initial insights into oxygen-transfer mechanisms. / Vallejos-Burgos, Fernando; Utsumi, Shigenori; Hattori, Yoshiyuki; García, Ximena; Gordon, Alfredo L.; Kanoh, Hirofumi; Kaneko, Katsumi; Radovic, Ljubisa R.

In: Fuel, Vol. 99, 01.09.2012, p. 106-117.

Research output: Contribution to journalArticle

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T1 - Pyrolyzed phthalocyanines as surrogate carbon catalysts

T2 - Initial insights into oxygen-transfer mechanisms

AU - Vallejos-Burgos, Fernando

AU - Utsumi, Shigenori

AU - Hattori, Yoshiyuki

AU - García, Ximena

AU - Gordon, Alfredo L.

AU - Kanoh, Hirofumi

AU - Kaneko, Katsumi

AU - Radovic, Ljubisa R.

PY - 2012/9/1

Y1 - 2012/9/1

N2 - Deposited and heat-treated phthalocyanines are promising electrocatalysts for replacing platinum in the oxygen reduction reaction (ORR), the most important process in energy conversion systems such as fuel cells; and yet its key mechanistic features are not well understood. To optimize their use, it is necessary to understand their behavior in the absence of an electric field. In the pursuit of this goal, we pyrolyzed metal-free, cobalt and copper phthalocyanines between 550 and 1000 °C and studied their structural and chemical changes by elemental analysis, N 2 and CO 2 adsorption, X-ray diffraction (XRD), Raman spectroscopy, X-ray analysis fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). Their catalytic activity was assessed by non-isothermal O 2 gasification and NO reduction reactions. A comparison of these results with their other properties allowed us to reach the following conclusions: (i) the loss of reactivity of metal-free phthalocyanine with heat treatment is attributed to its structural annealing and heteroatom loss, with the porosity changes having no effect; (ii) for metal phthalocyanines at intermediate heat treatment temperatures, the optimum in reactivity correlates with the micropore surface area and the presence of metal particles, with no influence of nitrogen content; (iii) the coordination metal increases phthalocyanine thermal stability in an inert atmosphere, but in an oxidizing atmosphere it acts as a gasification catalyst even below decomposition temperatures. The implications of these findings for catalytic oxygen-transfer mechanisms are discussed.

AB - Deposited and heat-treated phthalocyanines are promising electrocatalysts for replacing platinum in the oxygen reduction reaction (ORR), the most important process in energy conversion systems such as fuel cells; and yet its key mechanistic features are not well understood. To optimize their use, it is necessary to understand their behavior in the absence of an electric field. In the pursuit of this goal, we pyrolyzed metal-free, cobalt and copper phthalocyanines between 550 and 1000 °C and studied their structural and chemical changes by elemental analysis, N 2 and CO 2 adsorption, X-ray diffraction (XRD), Raman spectroscopy, X-ray analysis fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). Their catalytic activity was assessed by non-isothermal O 2 gasification and NO reduction reactions. A comparison of these results with their other properties allowed us to reach the following conclusions: (i) the loss of reactivity of metal-free phthalocyanine with heat treatment is attributed to its structural annealing and heteroatom loss, with the porosity changes having no effect; (ii) for metal phthalocyanines at intermediate heat treatment temperatures, the optimum in reactivity correlates with the micropore surface area and the presence of metal particles, with no influence of nitrogen content; (iii) the coordination metal increases phthalocyanine thermal stability in an inert atmosphere, but in an oxidizing atmosphere it acts as a gasification catalyst even below decomposition temperatures. The implications of these findings for catalytic oxygen-transfer mechanisms are discussed.

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Vallejos-Burgos F, Utsumi S, Hattori Y, García X, Gordon AL, Kanoh H et al. Pyrolyzed phthalocyanines as surrogate carbon catalysts: Initial insights into oxygen-transfer mechanisms. Fuel. 2012 Sep 1;99:106-117. https://doi.org/10.1016/j.fuel.2012.03.055