Air-Calcined Fe/Ni-Based Metal–Organic Framework Nanosheets for Oxygen Evolution Reactions

The oxygen evolution reaction (OER) plays a pivotal role in the hydrolysis process of zinc–air batteries. Consequently, it is essential to develop cathode catalysts with both cost-effectiveness and high oxygen evolution activity. In this study, we synthesized the FeFFIVE-1-Ni two-dimensional (2D) metal–organic framework (MOF) nanosheets via a straightforward solvothermal approach and oxidized them in an air atmosphere. During the calcination process in an air atmosphere, the heteroatoms (O, F) within the FeFFIVE-1-Ni 2D MOF nanosheets combine with iron and nickel metal ions, forming FeOF and NiF2 compounds. The synergy between these compounds and the creation of surface cracks during calcination yield catalytic active power and catalytic active sites essential for the oxygen evolution reaction. Notably, the overpotential of FeFFIVE-1-Ni 2D MOF nanosheets calcined in air under alkaline test conditions (η10 = 286 mV) was lower than that of commercial RuO2 catalysts (η10 = 355 mV). This work presents an effective strategy for replacing noble metal catalysts such as RuO2 by simply treating fluorinated metal–organic frameworks.