Deep electronic structure modulation of the self-deposited active layer on FeNi intermetallic compounds via an interfacial CeO₂ electron pump for efficient oxygen evolution reaction

Although FeNi intermetallic compounds (IMCs) are promising pre-catalysts for the oxygen evolution reaction (OER) due to their ability to in-situ form a stable Ni_1-xFe_xOOH active layer, their activity is ultimately limited by the saturation of Fe^{3 +}incorporation into the lattice. To overcome this limitation, we introduce CeO₂ as an external electron regulator to construct a carbon-coated heterostructure (C@CeO₂/FeNi). At the interface, CeO₂ acts as an electron pump, working synergistically with Fe³⁺ to enable deep electronic modulation of the self-deposited active layer, thereby breaking through the performance ceiling of FeNi IMCs. The optimal C@CeO₂/FeNi-0.3 catalyst achieves a low overpotential of only 211 mV at a current density of 10 mA cm⁻² and a small Tafel slope of 54 mV dec⁻¹ in 1.0 M KOH, significantly surpassing its CeO₂-free counterpart. In addition, it exhibits remarkable stability: after continuous electrolysis for 100 h at overpotentials of 230 and 350 mV, the activity of this material decays by only 10% and 8.3%, respectively. This work demonstrates that interfacial electron-pump engineering is an effective strategy to push the performance boundaries of alloy-based OER catalysts.