Phase Equilibrium Regulation in ZIF-67-Derived Electrocatalysts: Degradation Mechanism and Stability Enhancement for Oxygen Evolution Reaction.
basic_science · Level V
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- Record sourced from PubMed, PMID 40637194.
- Also identified by DOI 10.1021/acs.nanolett.5c02869.
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Abstract
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)<sub>2</sub>, 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)<sub>2</sub> to CoO, depleting the Co(OH)<sub>2</sub> reservoir required to sustain the active CoOOH phase via equilibrium dynamics. By lowering the reaction temperature (e.g., to 0 °C), Co(OH)<sub>2</sub> preservation improves stability, reducing overpotential increases after 5000 cycles to just 9 mV (10 mA cm<sup>-2</sup>) and 15 mV (100 mA cm<sup>-2</sup>), outperforming room-temperature performance. These insights highlight phase equilibrium regulation as a key strategy for enhancing the MOF-derived catalyst durability.