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Hierarchically Porous Nitrogen-Doped Carbon Nanotubes Derived from Core-shell ZnO@Zeolitic Imidazolate Framework Nanorods for Highly Efficient Oxygen Reduction Reactions

Abstract

Developing effective nitrogen-doped (N-doped) metal-free carbon nanotube electrocatalysts with high activity and stability to replace the scarce Pt-based catalysts for oxygen reduction reaction (ORR) is of great importance in energy conversion devices. The hierarchical porosity and the content of the nitrogen atoms in carbon nanotubes play important role for determining the active sites. The use of metal-organic frameworks (MOFs) as templates and/or precursors to fabricate porous carbons could inherit their merits including highly doped heteroatoms, large surface areas and controllable structures. Herein, core-shell ZnO@ZIF-8 nanorods were employed as templates and precursors to fabricate the hierarchically porous N-doped carbon nanotubes (NCNTs) using a self-sacrifice template approach. The high level of graphitization and nitrogen content of the NCNTs could be tuned by the core-shell ZnO@ZIF-8 nanorod precursors and pyrolysis temperature. The obtained hierarchically porous NCNTs exhibit superior performances for ORR in alkaline solutions. Impressively, the NCNT-24-800 that pyrolyzed at 800 oC exhibit excellent performance with a positive onset potential of 0.06 V (vs. Ag/AgCl) and a more positive half-wave potential at -0.103 V (vs. Ag/AgCl, a positive shift of 27 mV compared with Pt/C), a high diffusion-limited current density of 5.68 mA cm-2 at -0.8 V, which are comparable to the benchmark commercial 20 wt% Pt/C catalyst. Furthermore, compared with the traditional Pt/C, NCNTs show excellent long term stability and methanol tolerance. The self-sacrifice template approach could open up a new avenue toward the fabrication of materials with unique porous structure from MOFs as highly efficient metal-free electrocatalysts for ORR.

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Publication details

The article was received on 06 Apr 2017, accepted on 13 May 2017 and first published on 15 May 2017


Article type: Paper
DOI: 10.1039/C7TA02999C
Citation: J. Mater. Chem. A, 2017, Accepted Manuscript
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    Hierarchically Porous Nitrogen-Doped Carbon Nanotubes Derived from Core-shell ZnO@Zeolitic Imidazolate Framework Nanorods for Highly Efficient Oxygen Reduction Reactions

    P. Shi, J. Yi, T. Liu, L. Li, L. Zhang, C. Sun, Y. Wang, Y. Huang and R. Cao, J. Mater. Chem. A, 2017, Accepted Manuscript , DOI: 10.1039/C7TA02999C

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