Cation Migration-Induced Lattice Oxygen Oxidation in Spinel Oxide for Superior Oxygen Evolution Reaction

Activating the lattice oxygen can significantly improve the kinetics of oxygen evolution reaction (OER), however, it often results in reduced stability due to the bulk structure degradation. Here, we develop a spinel Fe_0.3Co_0.9Cr_1.8O₄ with active lattice oxygen by high-throughput methods, achieving high OER activity and stability, superior to the benchmark IrO₂. The oxide exhibits an ultralow overpotential (190 mV at 10 mA cm^-2) with outstanding stability for over 170 h at 100 mA cm^-2. Soft X-ray absorption- and Raman-spectroscopies, combined with ¹⁸O isotope-labelling experiments, reveal that lattice oxygen activation is driven by Cr oxidation, which induces a cation migration from CrO₆ octahedrons to CrO₄ tetrahedrons. The geometry conversion creates accessible non-bonding oxygen states, crucial for lattice oxygen oxidation. Upon oxidation, peroxo O-O bond is formed and further stabilized by Cr⁶⁺ (CrO₄ tetrahedra) via dimerization. This work establishes a new approach for designing efficient catalysts that feature active and stable lattice oxygen without compromising structural integrity.