Phase Equilibrium Regulation in ZIF-67-Derived Electrocatalysts: Degradation Mechanism and Stability Enhancement for...

Metal-organic frameworks (MOFs) like ZIF-67 are promising electrocatalysts due to their tunable structures and porosity, but their instability in aqueous electrolytes requires a deeper understanding. This study investigates the structural evolution and degradation mechanism of ZIF-67 during the oxygen evolution reaction (OER) in alkaline media. Using atomic-resolution identical-location transmission electron microscopy, we reveal its transformation pathway: ZIF-67 first converts to Co(OH)₂, then progressively evolves into catalytically active CoOOH and inactive CoO species, ultimately establishing a dynamic three-phase equilibrium under operational conditions. Prolonged cycling drives the irreversible conversion of Co(OH)₂ to CoO, depleting the Co(OH)₂ reservoir required to sustain the active CoOOH phase via equilibrium dynamics. By lowering the reaction temperature (e.g., to 0 °C), Co(OH)₂ preservation improves stability, reducing overpotential increases after 5000 cycles to just 9 mV (10 mA cm^-2) and 15 mV (100 mA cm^-2), outperforming room-temperature performance. These insights highlight phase equilibrium regulation as a key strategy for enhancing the MOF-derived catalyst durability.