Carbon nanotube growth on nanozirconia under strong cathodic polarization in steam and carbon dioxide

Youkun Tao, Sune Dalgaard Ebbesen, Wei Zhang, Mogens Bjerg Mogensen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Growth of carbon nanotubes (CNTs) catalyzed by zirconia nanoparticles was observed in the Ni-yttria doped zirconia (YSZ) composite cathode of a solid oxide electrolysis cell (SOEC) at approximately 875 °C during co-electrolysis of CO2 and H2O to produce CO and H 2. CNT was observed to grow under large cathodic polarizations specifically at the first 1 to 2 μm Ni-YSZ active cathode layer next to the YSZ electrolyte. High resolution transmission electron microscopy (HRTEM) shows that the CNTs are multi-walled with diameters of approximately 20 nm and the catalyst particles have diameters in the range of 5 to 25 nm. The results of HRTEM and energy dispersive X-ray spectroscopy (EDS) analysis confirm that the catalyst particles attached to the CNT are cubic zirconia. Most of the zirconia particles are located at one end of the CNTs, but particles embedded in the walls or inside the CNTs are also observed. Apart from the CNTs, graphitic layers covering zirconia nanoparticles are also widely observed. This work describes nano-zirconia acting as a catalyst for the growth of CNT during electrochemical conversion of CO2 and H2O in a Ni-YSZ cermet under strong cathodic polarization. An electrocatalytic mechanism is proposed for the CNT growth in SOECs. These findings provide further understanding not only on the mechanism of the catalytic growth of CNTs, but also on the local electrochemical properties of a highly polarized Ni-YSZ cathode at the micro and nano level. Zap it! This work describes nanozirconia acting as a catalyst for the growth of carbon nanotubes (CNTs) during electrochemical conversion of carbon dioxide and water in a nickel-yttria- stabilized zirconia cermet under strong cathodic polarization. An electrocatalytic mechanism is proposed for the growth of the CNTs. ${{{\rm {\rm V}}{{\cdot \cdot \hfill \atop {\rm {\rm o}}\hfill}}}} $=Oxygen vacancy, ${{{\rm {\rm O}}{{{\rm {\rm x}}\hfill \atop {\rm {\rm o}}\hfill}}}}$=occupied site of oxygen in zirconia. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Original languageEnglish
JournalChemCatChem
Volume6
Issue number5
Pages (from-to)1220-1224
Number of pages5
ISSN1867-3880
DOIs
Publication statusPublished - 2014

Keywords

  • carbon
  • electrocatalysis
  • nanotubes
  • solid oxide cells
  • zirconia
  • Carbon
  • Carbon dioxide
  • Catalysis
  • Catalysts
  • Cathodes
  • Cathodic polarization
  • Cermets
  • Electrocatalysis
  • High resolution transmission electron microscopy
  • Multiwalled carbon nanotubes (MWCN)
  • Nanoparticles
  • Nanotubes
  • Nickel
  • X ray spectroscopy
  • Yttria stabilized zirconia
  • Yttrium alloys
  • Carbon nanotube growth
  • Electrocatalytic mechanism
  • Electrochemical conversion
  • Energy dispersive X ray spectroscopy
  • Solid oxide electrolysis cells
  • Solid-oxide cells
  • Stabilized zirconia
  • Zirconia nanoparticles
  • Zirconia

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