Lattice oxygen-mediated Co–O–Fe formation in Co-MOF via Fe doping and ligand design for efficient oxygen evolution

The rational design of metal-organic frameworks (MOFs) provides potential opportunities for improving energy conversion efficiency. However, developing efficient MOF-based electrocatalysts remains highly challenging. Herein, a strategy involving strain engineering is developed to promote the electrocatalytic performance of MOFs by optimizing electronic configuration and improving the active site. As expected, the optimized CoFe–BDC-NO2 exhibits a low overpotential of 292 mV at 10 mA cm–2 and a small Tafel slope of 31.6 mV dec–1 as oxygen evolution reaction (OER) electrocatalyst. Notably, when CoFe–BDC-NO2 is prepared on Nickel foam (NF), the overpotential is only 345 mV at 1 A cm–2, which ensures efficient water oxidation properties. Integrating CoFe–BDC-NO2/NF anode in membrane electrode assembly (MEA) for overall water splitting and CO2 reduction reaction (CO2RR) tests, the results show that the cell voltages of CoFe–BDC-NO2/NF are 3.14 and 3.09 V at 300 mA cm–2 (25 ℃), respectively, indicating that MOFs have various practical application prospects. The research of the structure-performance relationship reveals the lattice oxygen oxidation mechanism (LOM) where the Co-O-Fe bond is formed during the OER process by changing the electronic environment and coordination structure of CoFe–BDC-NO2, and with high valence Co as active center, which provides a deep understanding of the structure design of MOFs and their structural transformation during OER.