Ferrocene-MOFs: Optimizing OER Kinetics for Water Splitting

Optimizing the adsorption and desorption kinetics of oxygen evolution reaction (OER) is crucial for efficient overall water splitting. Herein, we report a series of porous ferrocene-based metal–organic framework (MFc-MOF, M = Co, Ni, Fe, Mn) nanoflowers featuring a close π–π stacking lattice structure as model catalysts, and explore the structure–activity relationship. Operando electrochemical impedance spectroscopy implies that the synthesized CoFc-MOF@NF facilitates intermediate adsorption and desorption. It exhibits an ultralow overpotential of 189 mV at 10 mA cm–2 and maintains stability for 250 h. In an overall water splitting device, when CoFc-MOF@NF serves as the anode, it yields a significantly lower cell voltage than commercial RuO2 and shows excellent stability at 100 mA cm–2 for 100 h. In situ Raman spectroscopy reveals that the CoFc-MOF@NF surface transforms into CoFeOOH, the OER-active species, while preserving the MOF framework. The inner MOF's ferrocene units act as efficient electron-transfer mediators. These findings highlight CoFc-MOF@NF's potential as a leading catalyst for sustainable water splitting hydrogen production, combining high catalytic activity, rapid kinetics, and robust stability. This work presents a new approach to balance activity and stability in MOF-based OER catalysts.