ZIF-67 nanostructures anchored on 3D graphene sheets: a non-noble electrocatalyst for efficient oxygen evolution reaction

The efficiency of water electrolysis is heavily dependent on the oxygen evolution reaction. Overcoming the persistent challenge of developing electrocatalysts that exhibit high current density, low overpotential, and long-lasting performance is crucial. In this context, we introduce a promising electrocatalyst for water oxidation under alkaline conditions. This catalyst takes the form of a composite material composed of ZIF-67 and 3D graphene sheets, specifically designated as ZIF-67@3D graphene. 3D vertical graphene sheets were deposited on nickel foam (NF) using an inductively coupled plasma chemical vapor deposition system. ZIF-67 was synthesized via mechanical stirring, employing cobalt metal ions as the coordinating species, with 2-methylimidazole (2-MIM) serving as a ligand. The as-deposited 3D graphene sheets on nickel foam were integrated with a solution of ZIF-67 and subjected to stirring to yield the composite material. Our electrochemical investigation revealed that the ZIF-67@3D graphene composite displays enhanced catalytic performance compared to ZIF-67@NF. The composite exhibited an overpotential of 220 mV at a current density of 10 mA cm^-2, along with a Tafel slope of 170 mV dec^-1, in contrast to 290 mV at 10 mA cm^-2 and a Tafel slope of 174 mV dec^-1 for ZIF-67/NF alone. Additionally, the ZIF-67@3D graphene/NF composite achieved a current density of 50 mA cm^-2 with an overpotential of only 380 mV. This notable enhancement in performance is attributed to the synergistic interactions between the metal-organic framework and graphene, which result in an improved current density and a decreased overpotential.

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