Ferromagnetic Ni3+ center and built-in electric fields enable lattice oxygen activation for efficient electrocatalytic oxygen evolution

Despite considerable advances in water electrolysis, the oxygen evolution reaction (OER) remains the principal bottleneck. Herein, we tackle self-adaptive lattice oxygen activation by elucidating O–O coupling at the Ni₁@CoOOH(1 1 1)/C heterojunction, a highly efficient OER electrocatalyst with magnetic interfaces. Under alkaline conditions, spontaneous surface reconstruction from Ni₁@CoP(1 1 1)/C to Ni₁@CoOOH(1 1 1)/C heterojunctions takes place, where the carbon shell safeguards Ni and Co sites against oxidative dissolution and structural collapse. Different from the adsorbate evolution mechanism initially occurred at Ni₁@CoP(1 1 1)/C, lattice oxygen mechanism dominates on the magnetic Ni₁@CoOOH(1 1 1)/C heterojunction under alkaline conditions (pH = 14). The O−O coupling, presenting its rate-determining step, requires a predicted overpotential η of 0.238 V. First-principles calculations reveal that Jahn-Teller distortion occurred at the surficial ferromagnetic Ni³⁺ single-atom active center, together with the dynamic interfacial built-in electric fields in the Ni₁@CoOOH(1 1 1)/C heterojunction, synergistically drive O–O coupling. This finding provides critical insights into lattice oxygen activation under alkaline conditions and open promising avenues for the rational design of high-performance heterogeneous electrocatalysts.