Lattice Confinement of Cerium Dopants Via Quenching Enables D-Band Center Engineering for High-Performance Anion Exchange Membrane Water Electrolyzers

Lattice confinement of large-radius cerium enables atomic-level electronic modulation for oxygen evolution reaction (OER) electrocatalysts in anion exchange membrane water electrolyzer (AEMWE) applications but remains challenging. Herein, a metallic salt solution quenching strategy achieves lattice-confined cerium doping in iron sulfide composite nanoflowers (Fe9S10/FeS). The ultrafast cooling generates abundant grain boundaries and lattice strain, which collectively reduce FeFe orbital overlap, narrow the Fe d-band width, and shift the d-band center upward. These electronic modifications consequently optimize the adsorption energetics of oxygen-containing intermediates on the pristine Fe9S10/FeS surface, mitigating their excessively strong binding. According to density functional theory (DFT) calculations, the energy barrier for the rate-determining step is reduced from 2.22 eV to 1.82 eV. Consequently, the cerium-doped iron sulfide catalyst (Ce-FeS-4th) exhibits a low overpotential of 274 mV at 10 mA cm-2 and a Tafel slope of 68 mV dec-1. An AEMWE using this anode achieves 1.0 A cm-2 at 2.48 V and operates stably for over 300 h. Overall, this work establishes quenching-induced lattice confinement as a versatile paradigm for d-band center engineering in advanced electrocatalysts.