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1.
Nanoscale ; 12(28): 15115-15127, 2020 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-32657297

RESUMO

Hierarchical iron-nitrogen-codoped porous hollow carbon spheres have been synthesized by using melamine-formaldehyde (MF) resin spheres as templates, nitrogen sources and pore-forming agents. FeCl3, 1,10-phenanthroline and carbon black were used as iron, nitrogen and carbon sources. The as-obtained porous hollow carbon spheres possess a high specific surface area of 807 m2 g-1, as well as exhibited excellent electrocatalytic activity for the oxygen reduction reaction (ORR) in both acidic and alkaline media. In 0.1 M HClO4 solution, the onset potential was 0.857 V (vs. RHE) and the half-wave potential was 0.715 V, which are only 78 and 80 mV less than those of the 20% Pt/C catalyst, respectively. In addition, in 0.1 M KOH solution, the onset potential was 1.017 V and the half-wave potential was 0.871 V for the ORR, which are 22 and 28 mV more positive than those of the Pt/C catalyst, respectively. Meanwhile, the catalyst also exhibited excellent methanol tolerance and long-term durability with a more effective four-electron pathway compared to the 20% Pt/C catalyst in both acidic and alkaline media. When used as an air-cathode catalyst for a Zn-air battery, the maximum power density of a Zn-air battery with the MF-C-Fe-Phen-800 cathode was 235 mW cm-2 at a high current density of 371 mA cm-2, and a high open-circuit potential of 1.654 V, superior to that of Pt/C (199 mW cm-2, 300 mA cm-2, 1.457 V). A series of designed experiments suggested that the remarkable performance was attributed to the high specific area, hollow carbon spheres, unique hierarchical micro-mesoporous structures, high contents of pyridinic-N and graphitic-N. The superiority of the as-prepared catalyst makes it promising for use in practical applications.

2.
Macromol Rapid Commun ; 37(21): 1748-1753, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27717120

RESUMO

Highly conductive anion exchange membranes (AEMs), along with the ability to suppress swelling, are critical but challenging requirements for alkaline fuel cell applications. To achieve this criterion, a series of poly(ether sulfone)s (PESFs) with flexible alkyl imidazolium pendants attached directly on large planar 6,12-bis(4-hydroxyphenyl)-5,11-dihydroindolo[3,2-b]carbazole (DCP) units is reported. The planar DCP units stabilize the hydrophobic phase through strong π-π interactions and also facilitate the formation of ionic conducting channels through self assembly of hydrophilic pendants. The AEM prepared here, based on rational design, has a relatively low ion exchange capacity (IEC) of 1.86 × 10-3 mol g-1 and exhibits high hydroxide ion (OH- ) conductivity of 101 × 10-3 S cm-1 , a low swelling ratio of 9.3% and a water uptake of 39.6%. Furthermore, the AEMs reported in this paper have excellent stability in 1 m NaOH solution at 80 °C over 500 h. Therefore, the synthesized polymers offer a new insight into the design of high performance materials for AEMs.


Assuntos
Álcalis/química , Carbazóis/química , Fontes de Energia Elétrica , Polímeros/química , Sulfonas/química , Tamanho da Partícula , Polímeros/síntese química , Sulfonas/síntese química , Propriedades de Superfície
3.
Nanoscale ; 6(12): 6590-602, 2014 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-24806824

RESUMO

Nitrogen-doped graphitic porous carbons (NGPCs) have been synthesized by using a zeolite-type nanoscale metal-organic framework (NMOF) as a self-sacrificing template, which simultaneously acts as both the carbon and nitrogen sources in a facile carbonization process. The NGPCs not only retain the nanopolyhedral morphology of the parent NMOF, but also possess rich nitrogen, high surface area and hierarchical porosity with well-conducting networks. The promising potential of NGPCs as metal-free electrocatalysts for oxygen reduction reactions (ORR) in fuel cells is demonstrated. Compared with commercial Pt/C, the optimized NGPC-1000-10 (carbonized at 1000 °C for 10 h) catalyst exhibits comparable electrocatalytic activity via an efficient four-electron-dominant ORR process coupled with superior methanol tolerance as well as cycling stability in alkaline media. Furthermore, the controlled experiments reveal that the optimum activity of NGPC-1000-10 can be attributed to the synergetic contributions of the abundant active sites with high graphitic-N portion, high surface area and porosity, and the high degree of graphitization. Our findings suggest that solely MOF-derived heteroatom-doped carbon materials can be a promising alternative for Pt-based catalysts in fuel cells.

4.
J Am Chem Soc ; 132(48): 17056-8, 2010 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-21070073

RESUMO

In the present work, we have designed and synthesized a new highly durable iron phtalocyanine based nonprecious oxygen reduction reaction (ORR) catalyst (Fe-SPc) for polymer electrolyte membrane fuel cells (PEMFCs). The Fe-SPc, with a novel structure inspired by that of naturally occurring oxygen activation catalysts, is prepared by a nonpyrolyzing method, allowing adequate control of the atomic structure and surface properties of the material. Significantly improved ORR stability of the Fe-SPc is observed compared with the commercial Fe-Pc catalysts. The Fe-SPc has similar activity to that of the commercial Fe-Pc initially, while the Fe-SPc displays 4.6 times higher current density than that of the commercial Fe-Pc after 10 sweep potential cycles, and a current density that is 7.4 times higher after 100 cycles. This has been attributed to the incorporation of electron-donating functional groups, along with a high degree of steric hindrance maintaining active site isolation. Nonprecious Fe-SPc is promising as a potential alternative ORR electrocatalyst for PEMFCs.


Assuntos
Biomimética , Fontes de Energia Elétrica , Compostos Ferrosos/química , Indóis/química , Membranas Artificiais , Oxigênio/química , Polímeros/química , Catálise , Eletrólitos/química , Modelos Moleculares , Conformação Molecular , Oxirredução
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