Regulating the transformation behavior of nickel iron metal–organic frameworks through a dual-ligand strategy for enhanced oxygen evolution reaction performance

Two-dimensional (2D) 2,6-naphalene dicarboxylic acid-based nickel iron metal–organic frameworks (NiFe-NDC MOFs) have been widely deemed as promising electrocatalysts by virtue of their adorable specific surface area and the highly-exposed reactive metal centers. However, the practical performance of the pristine NiFe-NDC MOFs is far from satisfaction towards the electrocatalytic water oxidation for the sluggish ion-transport. Herein, we report a co-coordination approach to afford dual-ligand NiFe electrocatalysts (NiFe-NDC_xBDC_1-x) with striking oxygen evolution reaction (OER) performance. Except for the 2,6-naphalene dicarboxylic acid (NDC), 1,4-terephthalic acid (BDC) is adopted as the co-coordination ligand to tune the electronic and structural configuration of the catalysts via the unique ligand processability of the MOFs. The optimal NiFe-NDC_0.9BDC_0.1 displays a superior performance for OER catalysis with an overpotential of 295 mV when current density arrives at 10 mA cm⁻² and the Tafel slope is 69.4 mV dec^-1, as well as excellent stability in alkaline media. In-situ Raman and ex-situ X-ray photoelectron spectroscopy further indicates that introduction of BDC ligands not only strengthen the interaction between Ni and Fe atoms, but also facilitate the deeper conversion from MOF to active NiOOH species, especially the higher proportion of β-NiOOH species which can greatly promote the OER performance.