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Facile metal coordination of active site imprinted nitrogen doped carbons for the conservative preparation of non-noble metal oxygen reduction electrocatalysts

 
: Mehmood, Asad; Pampel, Jonas; Ali, Ghulam; Ha, Heungyong; Ruíz-Zepeda, Francisco; Fellinger, Tim-Patrick

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Advanced energy materials 8 (2018), No.9, Art. 1701771, 10 pp.
ISSN: 1614-6840
ISSN: 1614-6832
European Commission EC
FP7-NMP; 314515; EUROLIS
Advanced European lithium sulphur cells for automotive applications
English
Journal Article
Fraunhofer IWS ()
active site imprinting; FeN4 active site; metal-nitrogen coordination; non-noble metal catalyst; Oxygen Reduction Reaction

Abstract
Iron- or cobalt-coordinated heteroatom doped carbons are promising alternatives for Pt-based cathode catalysts in polymer-electrolyte fuel cells. Currently, these catalysts are obtained at high temperatures. The reaction conditions complicate the selective and concentrated formation of metal-nitrogen active sites. Herein a mild procedure is introduced, which is conservative toward the carbon support and leads to active-site formation at low temperatures in a wet-chemical metal-coordination step. Active-site imprinted nitrogen doped carbons are synthesized via ionothermal carbonization employing Lewis-acidic Mg2+ salt. The obtained carbons with large tubular porosity and imprinted N4 sites lead to very active catalysts with a half-wave potential (E1/2) of up to 0.76 V versus RHE in acidic electrolyte after coordination with iron. The catalyst shows 4e- selectivity and exceptional stability with a half-wave potential shift of only 5 mV after 1000 cycles. The X-ray absorption fine structure as well as the X-ray absorption near edge structure profiles of the most active catalyst closely match that of iron(II)phthalocyanine, proving the formation of active and stable FeN4 sites at 80 °C. Metal-coordination with other transition metals reveals that Zn-Nx sites are inactive, while cobalt gives rise to a strong performance increase even at very low concentrations.

: http://publica.fraunhofer.de/documents/N-477746.html