Molten Salt-Assisted Carbonization and Unfolding of Fe, Co-codoped ZIF-8 to Engineer Ultrathin Graphite Flakes for Bifunctional Oxygen Electrocatalysis

• Published in: Journal of alloys and compounds Vol. 920; p. 165437
• Main Authors: Chen, Yingjie, Gong, Chong, Meng, Xiangyu, Chen, Xing, Li, Guofu, Sun, Qiong, Pang, Beili, Zhang, Qian, Feng, Jianguang, Yu, Liyan, Dong, Lifeng
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 05.11.2022; Elsevier BV
• Subjects: Carbon; Carbonization; Catalysts; Chemical reduction; Cobalt; electrocatalyst; Electrocatalysts; Flakes (defects); Graphite; graphite flake; Iron; Metal air batteries; Metal-organic frameworks; Molten salts; NaCl; Nitrogen; Oxygen evolution reactions; Oxygen reduction reactions; Porosity; Pyrolysis; Structural hierarchy; Transition metals; unfolding; Zeolites; ZIF; Zinc-oxygen batteries; NaCl; electrocatalyst; graphite flake; ZIF; unfolding
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2022.165437

Zeolitic imidazolate frameworks (ZIFs) are already utilized to synthesis precursors for transition metal and nitrogen co-doped carbon catalysts. However, there are few reports on deliberately tailoring catalyst structure except for the hierarchical pores formed from Zn evaporation during the pyrolysis. Herein, NaCl salt-assisted carbonization and unfolding of Fe, Co-codoped ZIF-8 polyhedron (FeCo/ZIF-8) result in ultrathin Fe, Co, N-codoped graphite flake (FeCo/NG), while FeCo/ZIF-8 pyrolysis without NaCl yields Fe, Co, N-codoped carbon spheres (FeCo/NC). Because of the high specific surface area, porosity, and degree of defects, the active site is further exposed. The synthesized FeCo/NG demonstrates excellent oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) properties with half-wave potential (E1/2) at 0.88V and overpotential at 460mV and good cycling stability, superior to those of FeCo/NC. In addition, the assembled Zn-air batteries with FeCo/NG catalysts deliver high peak power density at 109mWcm-2, specific capacity at 783 mAh g-1 and an operating time for 100h. The study will provide a feasible synthesis method to design high-performance electrocatalysts by deliberate tailoring structures with molten salt-assisted carbonization and unfolding of ZIFs. [Display omitted] •Molten salt-assisted pyrolysis tailors ZIF-8 polyhedron into ultrathin graphite flake.•Molten NaCl assists carbonization and unfolding of FeCo/ZIF-8 to form ultrathin FeCo/NG.•Evaporation of Zn in pyrolysis and removal of NaCl result in porous FeCo/NG.•FeCo/NG demonstrates excellent bifunctional oxygen electrocatalytic performances.•Zn-air battery with FeCo/NG delivers high peak power density and specific capacity.