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Reducing the overpotential of oxygen evolution reaction (OER) with slow kinetics is important to realize commercial hydrogen production from water electrolysis. Here, ZnCo 2 O 4 with abundant surface oxygen vacancies is employed to clarify the influence of oxygen vacancies on OER performance under AC magnetic field. The additional active sites as well as enhanced reaction activity of each active sites resulting from oxygen vacancies enable N–ZnCo 2 O 4-δ -350 to exhibit outstanding OER performance, where the overpotential is 406 mV at 10 mA cm−2. Furthermore, double exchange interaction between Co2+-O2--Co3+ ignited by oxygen vacancies produces ferromagnetism in N–ZnCo 2 O 4-δ , which can directly promote OER under ACMF. And the mass transport at additional active sites active sites provided by oxygen vacancies is also accelerated under ACMF due to magnetohydrodynamic convection. As a result, non-iR-corrected overpotential at 10 mA cm−2 of N–ZnCo 2 O 4-δ -350 is reduced to 243 mV when the ACMF intensity is 4.752 mT, which is a 44.5% reduction compared to no ACMF. These findings provide a novel and efficient perspective for realizing efficient electrocatalysis. [Display omitted] • Oxygen vacancy (O v) can optimize e g occupancy and induce built-in electric field. • Double exchange interaction caused by O v produces ferromagnetism in Co2+-O2--Co3+. • The overpotential (η 10) of N–ZnCo 2 O 4-δ -350 is reduced by 44.5% at 4.752 mT. • OER enhancement under AC magnetic field is related to convection and ferromagnetism. [ABSTRACT FROM AUTHOR]