In Situ Tracking of Ni-MOF Reconstruction into Active Ni(OH)₂ OER Catalysts

The oxygen evolution reaction (OER) remains a key bottleneck in electrochemical energy storage and conversion. In this work, we demonstrate the transmutation of a Ni-based metal-organic framework (Ni-MOF), composed of one-dimensional Ni-(μ₃-OH)/(μ₂-H₂O)-Ni chains interconnected by 1,4-ndc linker, into catalytically active β-Ni(OH)₂. This top-down reconstruction strategy involves the disintegration of 1,4-ndc linker and transformation of 1D Ni-(μ₃-OH)/(μ₂-H₂O)-Ni chains (which act as precursors), into ultra-low-dimensional (thickness ∼ 1.5-2.6 nm), defect-rich β-Ni(OH)₂ structure. The activated catalyst achieves a low overpotential of 300 mV at 10 mA.cm^-2, surpassing commercial IrO₂. In situ Raman and powder diffraction studies demonstrate pH- and potential-dependent phase transitions, leading to the formation of catalytically active β-Ni(OH)₂. In situ X-ray absorption spectroscopy (XAS) confirms progressive structural evolution, with a Ni─O bond contraction from 2.06 to 1.89 Å under catalytic conditions, indicative of dynamic NiOOH phase formation. Density functional theory (DFT) calculations reveal that the exposed Ni²⁺ centers stabilize OER intermediates and facilitate the adsorbate oxygen evolution mechanism (AEM). The catalyst also demonstrates robust activity at elevated temperatures. This work provides extensive mechanistic insights into catalyst activation and introduces a novel strategy for designing high-performance MOF based OER electrocatalysts.