Mechanochemical Synthesis of Fluorine-Containing Co-Doped Zeolitic Imidazolate Frameworks for Producing Electrocatalysts

Catalysts derived from pyrolysis of metal organic frameworks (MOFs) are promising candidates to replace expensive and scarce platinum-based electrocatalysts commonly used in polymer electrolyte membrane fuel cells. MOFs contain ordered connections between metal centers and organic ligands. They can be pyrolyzed into metal- and nitrogen-doped carbons, which show electrocatalytic activity toward the oxygen reduction reaction (ORR). Furthermore, metal-free heteroatom-doped carbons, such as N-F-Cs, are known for being active as well. Thus, a carbon material with Co-N-F doping could possibly be even more promising as ORR electrocatalyst. Herein, we report the mechanochemical synthesis of two polymorphs of a zeolitic imidazole framework, Co-doped zinc 2-trifluoromethyl-1H-imidazolate (Zn0.9Co0.1(CF3-Im)(2)). Time-resolved in situ X-ray diffraction studies of the mechanochemical formation revealed a direct conversion of starting materials to the products. Both polymorphs of Zn0.9Co0.1(CF3-Im)(2) were pyrolyzed, yielding Co-N-F containing carbons, which are active toward electrochemical ORR.

Automated summary

Catalysts derived from pyrolysis of MOFs are potential alternatives to expensive and scarce platinum-based electrocatalysts in polymer electrolyte membrane fuel cells. By pyrolyzing MOFs, metal and nitrogen-doped carbons can be obtained, which show electrocatalytic activity towards ORR. In addition, metal-free heteroatom-doped carbons also exhibit activity. Therefore, carbon materials with Co-N-F doping may be more promising as ORR electrocatalysts.