Fabricating Co–N–C catalysts based on ZIF-67 for oxygen reduction reaction in alkaline electrolyte

Synthesis of high-efficiency and low-cost electrocatalysts for oxygen reduction reaction (ORR) to replace Pt or its alloys become one of the key factors of fuel cells. In this work, a typical Co–N–C catalyst from ZIF-67 was fabricated by pyrolyzing the as-prepared ZIF-67. The characteristic and performance of the obtained Co–N–C catalyst was analyzed by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer -Emmette-Teller (BET) method. The results show that the obtained catalyst was composed of rhombic dodecahedrons particles about 300 ​nm, which came from pyrolyzing ZIF-67 at 700 ​°C, synthesized with 1:6 ​M ratio of cobalt nitrate and 2-methylimidazole. In O 2 saturated 0.1 ​M KOH solution, the onset potential, half-wave potential and limiting current density of the catalyst were 0.91 ​V, 0.82 ​V, and 5.33 ​mA/cm 2 , behaving excellent electrochemical performance. These reasons such as exposing more Co–N active sites, more pyridinic nitrogen, even particles with rhombic dodecahedrons structure and larger specific surface area, contributed to its good catalytic activity. In the ZIF-67 frameworks of different sizes, the 300 ​nm ZIF-67-6 enhances ORR performance in alkaline medium. • The size-controlled was successfully fabricating. • The porous Co–N–C catalyst could be obtained by pyrolyzing the synthesized ZIF-67. • ZIF-67-700 of 300 ​nm had the excellent ORR performance.