Ligands Defect-Induced Structural Self-Reconstruction of Fe–Ni–Co-Hydroxyl Oxides with Crystalline/Amorphous Heterophase from a 2D Metal–Organic Framework for an Efficient Oxygen Evolution Reaction

The two-dimensional (2D) Fe–Ni–Co-MOF is synthesized using a simple double ligand strategy at room temperature. The surface reconstruction process transforms it into a crystalline–amorphous heterojunction composed of polycrystalline metal (oxy)hydroxide (MOOH) and amorphous metal oxides/hydroxides with terephthalic acid (TPA) by coordination covalent bonding. In situ Raman spectroscopy discloses the dynamic structure conversion. Density functional theory (DFT), Fourier transform infrared spectroscopy (FTIR), and solid-state nuclear magnetic resonance (SSNMR) reveal the induction of the ligand defects on surface reconstruction and the enhancing effect of TPA on the oxygen evolution reaction (OER) performance through a covalent interaction. The amorphous–crystalline heterojunction of Fe–Ni–CoOOH-TPA has numerous structural defects and high electrical conductivity, resulting in an efficient and stable OER performance with overpotentials of 236 mV at 10 mA cm –2 . It has also been observed that the catalyst processes self-healing in an idle state, arising from the reversible conversion of MOOH to M(OH) 2 . This work reveals the structural and compositional transformation of the 2D Fe–Ni–Co-MOF during surface reconstruction, elucidating the relationship between electrocatalytic reconstruction and water-splitting performance of metal–organic framework (MOF)-based catalysts. It has been proven that appropriate covalent interactions enhance the OER of electrocatalysts.