Cobalt Imidazolate Framework as Precursor for Oxygen Reduction Reaction Electrocatalysts

Abstract

Käfigtransport: Die Aufnahme von H2‐Molekülen in H2O‐Käfige unter Bildung von Wasserstoff‐Clathrat‐Hydraten eröffnet neue Möglichkeiten für die Speicherung und den Transport von Wasserstoff. Reine H2‐Cluster lassen sich jedoch nur unter hohem Druck im Clathrat‐Hydrat stabilisieren. Abhilfe schafft die Einführung von THF als zweitem Gastmolekül, das den erforderlichen Druck von 220 MPa auf 5 MPa verringert (Bild: H2/THF‐Hydrat; blau THF, rot H2).

Effect of ZIF-8 Crystal Size on the O2 Electro-Reduction Performance of Pyrolyzed Fe–N–C Catalysts

“…Rational approaches for the selection of metal, nitrogen and carbon precursors, for the synthetic conditions and for more durable Metal-N-C catalysts, are, however, still needed. In 2011, the use of metal organic frameworks (MOFs) as sacrificial N and C precursors for the synthesis of Co-and Fe-N-C catalysts was first reported [8,13]. In the approach by Liu's group, the cobalt ions were engaged in the MOF structure and therefore ideally dispersed and coordinated to nitrogen atoms [13].…”

“…In 2011, the use of metal organic frameworks (MOFs) as sacrificial N and C precursors for the synthesis of Co-and Fe-N-C catalysts was first reported [8,13]. In the approach by Liu's group, the cobalt ions were engaged in the MOF structure and therefore ideally dispersed and coordinated to nitrogen atoms [13]. The inherent disadvantage is the high content of cobalt in Co-based MOFs, 30-40 wt.…”

“…% [7,[14][15][16]. Too large Fe or Co contents lead to the formation of highly graphitized carbon structures during pyrolysis [13,17]. In such graphitized structures, the number of MeNxCy active sites is low, which leads to a low ORR activity [18,19].…”

“…Other Fe-and Fe-Co-N-C catalysts pyrolyzed in inert atmosphere have resulted in a constant current density at 0.4-0.5 V over several hundred hours of operation in PEMFC, a promising achievement toward more durable Me-N-C catalysts [9,31]. Since the first reports on the synthesis of Metal-N-C materials via the sacrificial pyrolysis of microporous ZIFs [8,13], modifications of the preparation of the catalyst precursor from Fe(II) acetate, N-ligands and ZIF-8 have minimized the formation of undesired iron particles during pyrolysis. Low energy milling of the dry precursor powders has been shown to optimise the dispersion of ferrous ions and to favour the formation of FeNxCy moieties during pyrolysis [25,32].…”

MOF-reduced Graphene Oxide Composites with Enhanced Electrocatalytic Activity for Oxygen Reduction Reaction

“…Metal-organic frameworks (MOFs) are built from the reaction of metal ions and organic ligands, which have the advantage of particular porous structures and high specific surface area [9]- [11]. It has caught attention of plenty of researchers in gas adsorption [12]- [14], storage [15][16][17], sensors [10] and catalysis [18], [19]. Moreover, zeolitic imidazolate framework (ZIFs) could be designed with abundant metal-N x coordinate moieties that can improve electro-catalytic performance [20].…”