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.