Electronic modulation of cobalt active sites via copper doping in ferrocene-based metal-organic frameworks for enhanced oxygen evolution reaction

Modulating the electronic states of metal active sites offers a promising strategy for optimizing the electrocatalytic performance of MOF-based materials in the energy chemistry field. Here an efficient CoCuFc-MOF catalyst was synthesized by in situ introduction of copper ions during the synthesis process of CoFc-MOF via solvothermal method. The findings indicate that while the coordination configuration of CoFc-MOF remains preserved, the electronic structure of cobalt catalytic sites undergoes modulation through electron adsorption effect induced by copper atom doping. Thus, the optimized Cu₁Co₂Fc-MOF exhibits a 238 mV OER overpotential at 10 mA·cm⁻², and a 48.4 mV dec⁻¹ Tafel slope. Furthermore, only 5 % increase of overpotential is observed during 24 h durability test and a lower voltage of 1.686 V is needed to perform overall water splitting experiment. Surprisingly, DFT computations disclose that copper integration within the CoFc-MOF architecture significantly modulates the electronic configuration of cobalt active sites, consequently restructuring the rate-limiting mechanism in the OER pathway. It dramatically reduces the theoretical overpotential from 0.546 V in Cu₁Co₄Fc-MOF to 0.173 V in Cu₁Co₂Fc-MOF by converting OER rate-determining step from *OOH to O₂ to *OH to *O.