Redox-mediated oxygen evolution reaction: Engineering oxygen vacancies and heterojunctions in CeFeCo-UiO-66/layered...

Modifying metal-organic frameworks (MOFs)-based electrocatalysts remains crucial for enhancing oxygen evolution reaction (OER) performance. Although oxygen vacancies (V_O) are recognized as important for OER, their concentration control and relationship with catalytic activity remain unclear. In this study, we employ the redox potential difference between Co^2+/3+ (0.55 eV) and Ce^3+/4+ (1.44 eV) to induce corrosion on iron foam (IF), driving the redox reaction Ce⁴⁺ + Co²⁺ → Ce³⁺ + Co³⁺ to generate V_O. The V_O content can be qualitatively controlled by adjusting corrosion time, as verified by electron paramagnetic resonance (EPR). The CeFeCo-UiO-66/LDH catalyst delivers exceptional catalytic activity (overpotential η = 273 ± 3 mV @ 100 mA cm^-2). Combined X-ray photoelectron spectroscopy (XPS), EPR, in-situ Raman, and Density functional theory (DFT) analyses reveal that the redox interaction between Ce and Co generates V_O. These V_O species facilitate the formation of active CoOOH during the OER. This work offers insights for designing V_O engineering strategies in electrocatalytic systems.