Mössbauer transmission and back scattered conversion electron study of Fe nanowires encapsulated in multiwalled carbon nanotubes

Ruskov, T.; Asenov, S.; Spirov, I.; García, Cristhian; Mönch, Ingolf; Graff, Andreas; Kozhuharova, R.; Leonhardt, A.; Mühl, Thomas; Ritschel, M.; Schneider, Claus M.; Groudeva‐Zotova, S.

doi:10.1063/1.1811781

Cited by 40 publications

(30 citation statements)

References 13 publications

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“…Meanwhile, 57 Fe transmission Mössbauer spectroscopy (TMS) was also applied, which is a useful method to analyze the containing of different Fe phase [13].…”

Section: Methodsmentioning

confidence: 99%

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The structural evolution of thin multi-walled carbon nanotubes during isothermal annealing

Chen¹,

Shan²,

Tsukada³

et al. 2007

Carbon

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Systematic isothermal annealing has been carried out on catalytic chemical vapor deposition-derived highly disordered multi-walled carbon nanotubes in order to understand the structural evolution of carbon nanotubes kinetically. After specified isothermal time the crystallographic parameters strongly depend on annealing temperature, and can be divided into three stages. Rapid structural enhancement in the range from 1800 to 2200°C originates from the abrupt evolution of the residual catalytic compounds and is seen as partially aligned small fringes along the tube length. The lack of further structural ordering at temperatures above 2400°C and the low activation energy (ca. 90kJ/mol) are thought to be the result of the limited space available for further structural development considering the nano-sized multi-walled carbon nanotubes.2

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“…Meanwhile, 57 Fe transmission Mössbauer spectroscopy (TMS) was also applied, which is a useful method to analyze the containing of different Fe phase [13].…”

Section: Methodsmentioning

confidence: 99%

“…13 The resultant linear relation of the plot ln(k) as a function of 1/T (Fig. (8)) provides the estimation of the apparent activation energy as the order of 90 kJ/mol for graphitization of our MWNTs in the temperature range from 1800 to 2600°C.…”

Section: K=a Exp(-e/rt)mentioning

confidence: 99%

The structural evolution of thin multi-walled carbon nanotubes during isothermal annealing

Chen¹,

Shan²,

Tsukada³

et al. 2007

Carbon

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“…13a). 63 The spectral areas of these two components represent only 10% (Table I), demonstrating that the major fraction of iron atoms in pristine Fe-N-C is engaged in molecular-like FeN x C y moieties. Figures 13b and 13c show the spectra after peroxide treatment with 2 · 10 −3 and 10 −2 mol H 2 O 2 mg −1 , respectively.…”

Section: 57mentioning

confidence: 99%

Degradation by Hydrogen Peroxide of Metal-Nitrogen-Carbon Catalysts for Oxygen Reduction

Goellner

Armel

Zitolo

et al. 2015

J. Electrochem. Soc.

180

168

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Fe-N-C and Co-N-C materials are promising catalysts for reducing oxygen in fuel cells. The degradation of such catalysts induced by H 2 O 2 was investigated by contacting them ex situ with various amounts of H 2 O 2 . The degradation increased with increasing amounts of H 2 O 2 . The effect was most severe for Cr-N-C followed by Fe-N-C and last by Co-N-C. Treatment with H 2 O 2 leads to diminished oxygen reduction activity at high potential and/or reduced transport properties at high current density in fuel cell. From spectroscopic characterization, it was found that 66 and 80% of the CoN x C y and FeN x C y moieties present in pristine catalysts survived the extensive H 2 O 2 treatment, respectively. In parallel, the activity for oxygen reduction was divided by ca 6-10 for Fe-N-C and by ca 3 for Co-N-C. The results suggest that the main degradation mechanism in fuel cell for such catalysts is due to a chemical reaction with H 2 O 2 that is generated during operation. The super-proportional decrease of the oxygen reduction activity with loss of FeN x C y and CoN x C y moieties suggests either that only a small fraction of such moieties are initially located on the top surface, or that their turnover frequency for oxygen reduction was drastically reduced due to surface oxidation by H 2 O 2 .

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“…However, it is impossible for annealed tube after the catalyst particle disappeared (the insert in On the other hand, 57 Fe TMS at room temperature is known as the sensitive tool to detect the composition of iron phases entrapped in carbon nanotubes [24][25][26]. As shown in Fig.…”

Section: Variation Of the Residual Fe Catalysts During Thermal Treatmmentioning

confidence: 99%

Removal of entrapped iron compounds from isothermally treated catalytic chemical vapor deposition derived multi-walled carbon nanotubes

Chen¹,

Kuno

Matsuo

et al. 2008

Carbon

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We have monitored the compositional changes of the residual metallic compounds in isothermally treated catalytic chemical vapor deposition derived multi-walled carbon nanotubes systematically using 57 Fe transmission Mössbauer and X-ray fluorescence. The iron phases entrapped in the as-synthesized carbon nanotubes consist of γ-iron, α-iron, Fe 3 C and Fe 1-x S. The Fe 1-x S phase decomposes completely around 1500 °C while the iron carbide phase decomposes in the temperature range of 1500 -2400 °C. The obtained apparent activation energy of ca. 76 kcal/mol suggests that the entrapped iron was removed via a diffusion process during thermal treatment.

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Mössbauer transmission and back scattered conversion electron study of Fe nanowires encapsulated in multiwalled carbon nanotubes

Cited by 40 publications

References 13 publications

The structural evolution of thin multi-walled carbon nanotubes during isothermal annealing

The structural evolution of thin multi-walled carbon nanotubes during isothermal annealing

Degradation by Hydrogen Peroxide of Metal-Nitrogen-Carbon Catalysts for Oxygen Reduction

Removal of entrapped iron compounds from isothermally treated catalytic chemical vapor deposition derived multi-walled carbon nanotubes

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