Tailoring the Magnetic‐Field‐Assisted Oxygen Evolution Reaction Activity of Sr ₃ YCo ₄ O ₁₂₋

The room‐temperature ferromagnetic Sr ₃ YCo ₄ O _{12− δ} (314‐SYCO) provides an ideal platform for investigating magnetic‐field‐assisted catalytic performance. Herein, a series of 314‐SYCO polycrystals were synthesized via a sol–gel route by systematically varying the sintering temperature (800, 1000, and 1200 °C) and duration (5–20 h) to elucidate the effects of thermal history on Co valence states, ferromagnetic properties, and magnetic‐field‐enhanced oxygen evolution reaction (OER) activity. At 1000 °C, extending the sintering duration from 5 to 20 h yields an ordered tetragonal phase, accompanied by a significant increase in the Co ³⁺ fraction from 73.3% to 98.6%. The Curie temperature reaches ~336 K at 15 h, while the 20 h sample exhibits a near‐saturation magnetization of 5.07 emu g ⁻¹ , nearly twice that of the 5 and 10 h samples. Under a 200 mT magnetic field, the OER kinetics exhibit a pronounced ferromagnetism‐dependent enhancement, leading to reductions in overpotential of 8.0–19.7 mV at 10 mA cm ⁻² . The sample sintered for 20 h exhibits the best performance, achieving a minimum overpotential of 343.8 mV together with a significant enhancement in intrinsic specific activity. Optimization of the sintering process effectively tunes the Co valence states and ferromagnetic ordering of 314‐SYCO, thereby enhancing magnetic‐field‐assisted OER activity.