Zeolitic Imidazole Frameworks-8 (ZIF-8) Modified with Cu(II)/Ni(II)/Co(II) As Bifunctional ORR/OER Electrocatalytic Material

Zeolitic Imidazole Frameworks-8 (ZIF-8) have been modified with transition metals by partially replacing the original Zn(II) metal ions with Co(II), Cu(II), or Ni(II) ions to form 50%-Co(II)/Ni(II)/Cu(II)/ZIF-8. The modification aims to create a material with a higher surface area, which is beneficial for use as an electrocatalyst. Among these MOFs, Co-modified ZIF-8 has shown the most potential electrocatalytic activity toward the oxygen reduction reaction (ORR) compared to nickel or copper modifications. Rotating ring-disk electrode (RRDE) measurements revealed kinetic parameters such as onset potential, kinetic current density, Tafel slope, and electron transfer number, offering insights into the reaction mechanism. 50%-Co(II)/ZIF demonstrated the best performance as an efficient ORR catalyst, with an onset potential of 0.8 V vs RHE and an electron transfer number reaching 3.43 at 0.7 V vs RHE, indicating a tendency towards a four-electron pathway. Chronoamperometry and 100 cycles of cyclic voltammetry measurements provided evidence of the stability of the material. Additionally, 50%-Co(II)/ZIF/C exhibited a decent overpotential of 0.509 V to achieve a current density of 10 mA cm-2 for oxygen evolution reaction (OER) catalysis.