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Facile synthesis of Co/Pd supported by few-walled carbon nanotubes as an efficient bidirectional catalyst for improving the low temperature hydrogen storage properties of magnesium hydride

Journal Article


Abstract


  • Catalytic doping is important for enhancing the hydrogen storage performance of metal hydrides, but it is challenging to develop a single catalyst to enhance both hydrogen desorption and absorption to a certain degree. Herein, a bidirectional Co/Pd catalyst, homogeneously loaded on bamboo-shaped carbon nanotubes (Co/Pd@B-CNTs), showed superior catalytic effects, improving both the hydrogen desorption and absorption properties of MgH 2 at relatively low temperatures. The MgH 2 -Co/Pd@B-CNTs composite starts to release hydrogen at 198.9 °C, which is 132.4 °C lower than as-milled MgH 2 . The hydrogen desorption activation energy for MgH 2 is reduced from 178.00 to 76.66 kJ mol -1 by the catalytic effects of Co/Pd@B-CNTs. The MgH 2 -Co/Pd@B-CNTs composite shows dramatically improved absorption kinetics; it rapidly uptakes 6.68 wt% H 2 within 10 s at 250 °C, and quickly absorbs 1.91 wt% H 2 within 100 s, even at a temperature as low as 50 °C. More importantly, a special mechanism for the "bidirectional catalyst" Co/Pd is proposed for the first time and discussed in detail. During the hydrogenation process, elemental Pd plays a dominant role in accelerating the preferential diffusion of hydrogen atoms at the Pd/Mg interface, while during dehydrogenation, phase transformation between Mg 2 Co and Mg 2 CoH 5 as well as a Mg-Pd alloy becomes the crucial factor, facilitating the release of hydrogen atoms by decreasing the diffusion barrier. Moreover, novel structures of bamboo-shaped carbon nanotubes with a large diameter (>100 nm) and high specific surface area (146.8 m 2 g -1 ) allow the homogenous dispersion of Co/Pd NPs and enhance the direct contact with MgH 2 particles.

Authors


  •   Liu, Meijia (external author)
  •   Xiao, Xuezhang (external author)
  •   Zhao, Shuchun (external author)
  •   Chen, Man (external author)
  •   Mao, Jianfeng
  •   Luo, Bosang (external author)
  •   Chen, Lixin (external author)

Publication Date


  • 2019

Citation


  • Liu, M., Xiao, X., Zhao, S., Chen, M., Mao, J., Luo, B. & Chen, L. (2019). Facile synthesis of Co/Pd supported by few-walled carbon nanotubes as an efficient bidirectional catalyst for improving the low temperature hydrogen storage properties of magnesium hydride. Journal of Materials Chemistry A, 7 (10), 5277-5287.

Scopus Eid


  • 2-s2.0-85062627279

Ro Metadata Url


  • http://ro.uow.edu.au/aiimpapers/3543

Number Of Pages


  • 10

Start Page


  • 5277

End Page


  • 5287

Volume


  • 7

Issue


  • 10

Place Of Publication


  • United Kingdom

Abstract


  • Catalytic doping is important for enhancing the hydrogen storage performance of metal hydrides, but it is challenging to develop a single catalyst to enhance both hydrogen desorption and absorption to a certain degree. Herein, a bidirectional Co/Pd catalyst, homogeneously loaded on bamboo-shaped carbon nanotubes (Co/Pd@B-CNTs), showed superior catalytic effects, improving both the hydrogen desorption and absorption properties of MgH 2 at relatively low temperatures. The MgH 2 -Co/Pd@B-CNTs composite starts to release hydrogen at 198.9 °C, which is 132.4 °C lower than as-milled MgH 2 . The hydrogen desorption activation energy for MgH 2 is reduced from 178.00 to 76.66 kJ mol -1 by the catalytic effects of Co/Pd@B-CNTs. The MgH 2 -Co/Pd@B-CNTs composite shows dramatically improved absorption kinetics; it rapidly uptakes 6.68 wt% H 2 within 10 s at 250 °C, and quickly absorbs 1.91 wt% H 2 within 100 s, even at a temperature as low as 50 °C. More importantly, a special mechanism for the "bidirectional catalyst" Co/Pd is proposed for the first time and discussed in detail. During the hydrogenation process, elemental Pd plays a dominant role in accelerating the preferential diffusion of hydrogen atoms at the Pd/Mg interface, while during dehydrogenation, phase transformation between Mg 2 Co and Mg 2 CoH 5 as well as a Mg-Pd alloy becomes the crucial factor, facilitating the release of hydrogen atoms by decreasing the diffusion barrier. Moreover, novel structures of bamboo-shaped carbon nanotubes with a large diameter (>100 nm) and high specific surface area (146.8 m 2 g -1 ) allow the homogenous dispersion of Co/Pd NPs and enhance the direct contact with MgH 2 particles.

Authors


  •   Liu, Meijia (external author)
  •   Xiao, Xuezhang (external author)
  •   Zhao, Shuchun (external author)
  •   Chen, Man (external author)
  •   Mao, Jianfeng
  •   Luo, Bosang (external author)
  •   Chen, Lixin (external author)

Publication Date


  • 2019

Citation


  • Liu, M., Xiao, X., Zhao, S., Chen, M., Mao, J., Luo, B. & Chen, L. (2019). Facile synthesis of Co/Pd supported by few-walled carbon nanotubes as an efficient bidirectional catalyst for improving the low temperature hydrogen storage properties of magnesium hydride. Journal of Materials Chemistry A, 7 (10), 5277-5287.

Scopus Eid


  • 2-s2.0-85062627279

Ro Metadata Url


  • http://ro.uow.edu.au/aiimpapers/3543

Number Of Pages


  • 10

Start Page


  • 5277

End Page


  • 5287

Volume


  • 7

Issue


  • 10

Place Of Publication


  • United Kingdom