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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.
Han et al. (Thu,) studied this question.