Selenium Vacancy‐Enabled High Spin‐Polarized Cobalt Sites to Effectively Mediate Spin Flipping in Oxygen Electrocatalysis

ABSTRACT Spin polarization of metal active centers provides a powerful means to mitigate the spin flipping of key intermediates during electrocatalysis. However, effectively triggering spin polarization and establishing its relationship with performance in oxygen reduction/evolution reactions (ORR/OER) remain challenging. This study proposes a defect engineering means that creates selenium vacancies (Se V ) in cobalt diselenide (CoSe 2 ) integrated onto an iron single‐atom platform (Fe SA @CoSe 2 ‐Se V ) to enhance Co's spin polarization. Fe SA @CoSe 2 ‐Se V achieves a high ORR half‐wave potential (0.921 V) and a low OER overpotential (370 mV@10 mA cm −2 ), significantly outperforming Fe SA @CoSe 2 . When applied to zinc‐air battery (ZAB), it achieves a high power‐density (186 mW cm −2 ), with a cycling life of up to 582 h. Fe SA @CoSe 2 ‐Se V ‐based flexible ZAB maintains stable charge/discharge performance even under 0°–180° bending conditions. Introduction of Se V reduces the degeneracy of the Co 3 d orbitals, effectively triggering spin polarization. This electronic structure reconstruction causes the π* orbital of Co‐*O/*OH to lose an electron, enhancing the hybridization between Co 3 d and *O/*OH 2 p orbitals and thereby mitigating the intermediates' spin flipping. Ferromagnetic Fe SA stabilizes the Se V and Co active sites, ensuring the structural/catalytic stability. This work confirms the effectiveness of Se V ‐induced spin polarization regulation, providing a novel spintronics‐based approach for designing bifunctional electrocatalysts.