Density functional theory study of oxygen reduction mechanism at nitrogen-doped carbon nanotubes for fuel cell applications

W. Y. Wong, Wan Ramli Wan Daud

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Nitrogen-doped carbon nanotubes (NCNT) have been found to be active towards oxygen reduction reaction (ORR) in fuel cell cathode through experimental study. The catalytic active NCNT was found to contain highest ratio of nitrogen bonded as pyridinic-N with carbon. Density functional theory was applied in this study to validate the active sites and reaction mechanisms on the NCNT surface determined from the experiments. In this study, three models of NCNTs differing from the nitrogen bonding natures in carbon nanotubes, namely pyridinic-N, quaternary-N and pyridinic-N-oxides were simulated individually. Mulliken population analysis and electron density mapped onto the surface of NCNT were included in the calculation to examine the active sites of NCNT for oxygen reduction process. To investigate the oxygen reduction mechanism, four hydrogen ions were added to the system subsequently and the adsorption energy for each reaction step was calculated. Simulation results showed that NCNT with pyridinic-N bonding nature exhibited the greatest charge distortion on the NCNT surface with the most exothermic adsorption energy (-0.46 eV) obtained when oxygen chemisorbed on the surface. The dominant pathway of the ORR reaction was found to proceed via pseudo-four electron transfer with the production of hydrogen peroxide as intermediate species before further reduction to water molecule. The varying binding energy in each reaction step qualitatively agrees with the experimental results.

Original languageEnglish
Pages (from-to)68-77
Number of pages10
JournalJournal of Engineering Science and Technology
Volume10
Issue numberSpec.issue8
Publication statusPublished - 2015

Fingerprint

Density functional theory
Fuel cells
Carbon nanotubes
Nitrogen
Oxygen
Adsorption
Binding energy
Hydrogen peroxide
Carrier concentration
Cathodes
Hydrogen
Molecules
Carbon
Oxides
Electrons
Ions
Water

Keywords

  • Density functional theory
  • Fuel cell
  • Nitrogen-doped Carbon Nanotubes
  • Oxygen reduction reaction

ASJC Scopus subject areas

  • Engineering(all)

Cite this

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abstract = "Nitrogen-doped carbon nanotubes (NCNT) have been found to be active towards oxygen reduction reaction (ORR) in fuel cell cathode through experimental study. The catalytic active NCNT was found to contain highest ratio of nitrogen bonded as pyridinic-N with carbon. Density functional theory was applied in this study to validate the active sites and reaction mechanisms on the NCNT surface determined from the experiments. In this study, three models of NCNTs differing from the nitrogen bonding natures in carbon nanotubes, namely pyridinic-N, quaternary-N and pyridinic-N-oxides were simulated individually. Mulliken population analysis and electron density mapped onto the surface of NCNT were included in the calculation to examine the active sites of NCNT for oxygen reduction process. To investigate the oxygen reduction mechanism, four hydrogen ions were added to the system subsequently and the adsorption energy for each reaction step was calculated. Simulation results showed that NCNT with pyridinic-N bonding nature exhibited the greatest charge distortion on the NCNT surface with the most exothermic adsorption energy (-0.46 eV) obtained when oxygen chemisorbed on the surface. The dominant pathway of the ORR reaction was found to proceed via pseudo-four electron transfer with the production of hydrogen peroxide as intermediate species before further reduction to water molecule. The varying binding energy in each reaction step qualitatively agrees with the experimental results.",
keywords = "Density functional theory, Fuel cell, Nitrogen-doped Carbon Nanotubes, Oxygen reduction reaction",
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AU - Wong, W. Y.

AU - Wan Daud, Wan Ramli

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N2 - Nitrogen-doped carbon nanotubes (NCNT) have been found to be active towards oxygen reduction reaction (ORR) in fuel cell cathode through experimental study. The catalytic active NCNT was found to contain highest ratio of nitrogen bonded as pyridinic-N with carbon. Density functional theory was applied in this study to validate the active sites and reaction mechanisms on the NCNT surface determined from the experiments. In this study, three models of NCNTs differing from the nitrogen bonding natures in carbon nanotubes, namely pyridinic-N, quaternary-N and pyridinic-N-oxides were simulated individually. Mulliken population analysis and electron density mapped onto the surface of NCNT were included in the calculation to examine the active sites of NCNT for oxygen reduction process. To investigate the oxygen reduction mechanism, four hydrogen ions were added to the system subsequently and the adsorption energy for each reaction step was calculated. Simulation results showed that NCNT with pyridinic-N bonding nature exhibited the greatest charge distortion on the NCNT surface with the most exothermic adsorption energy (-0.46 eV) obtained when oxygen chemisorbed on the surface. The dominant pathway of the ORR reaction was found to proceed via pseudo-four electron transfer with the production of hydrogen peroxide as intermediate species before further reduction to water molecule. The varying binding energy in each reaction step qualitatively agrees with the experimental results.

AB - Nitrogen-doped carbon nanotubes (NCNT) have been found to be active towards oxygen reduction reaction (ORR) in fuel cell cathode through experimental study. The catalytic active NCNT was found to contain highest ratio of nitrogen bonded as pyridinic-N with carbon. Density functional theory was applied in this study to validate the active sites and reaction mechanisms on the NCNT surface determined from the experiments. In this study, three models of NCNTs differing from the nitrogen bonding natures in carbon nanotubes, namely pyridinic-N, quaternary-N and pyridinic-N-oxides were simulated individually. Mulliken population analysis and electron density mapped onto the surface of NCNT were included in the calculation to examine the active sites of NCNT for oxygen reduction process. To investigate the oxygen reduction mechanism, four hydrogen ions were added to the system subsequently and the adsorption energy for each reaction step was calculated. Simulation results showed that NCNT with pyridinic-N bonding nature exhibited the greatest charge distortion on the NCNT surface with the most exothermic adsorption energy (-0.46 eV) obtained when oxygen chemisorbed on the surface. The dominant pathway of the ORR reaction was found to proceed via pseudo-four electron transfer with the production of hydrogen peroxide as intermediate species before further reduction to water molecule. The varying binding energy in each reaction step qualitatively agrees with the experimental results.

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KW - Nitrogen-doped Carbon Nanotubes

KW - Oxygen reduction reaction

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