Spinel　oxides,　representing　an　emerging　class　of　highly　active　catalysts　for　oxygen　evolution　(OER),　suffer　from　weak　covalency　of　metal　d　and　oxygen　p　orbitals　from　their　typical　crystal　structure,　which　generally　proceeds　the　OER　with　an　adsorbate　evolution　mechanism　(AEM)　pathway.　For　activating　the　lattice　oxygen　in　spinel　oxides　to　bypass　the　scaling　relationship　limitation　of　AEM,　we　herein　grow　the　sulfate　salts　on　the　octahedral　sites　of　spinel　NiFe2O4　to　introduce　the　Ni4+　cations　and　Ni　vacancies　in　octahedral　sites,　which　exhibit　remarkable　OER　performance　with　an　overpotential　of　293　mV　at　500　mA　cm-2.　Experiments　and　theoretical　calculations　reveal　that　the　formation　Ni4+　cations　and　Ni　vacancies　jointly　enhance　the　metal-oxygen　hybridization　and　strengthen　the　metal-oxygen　bond　covalency　in　both　NiFe2O4　and　NiFeOOH　phases,　activating　the　lattice　oxygen　and　successfully　triggering　the　lattice　oxygen　mechanism　(LOM)　pathway　on　spinel　oxides.　©　2023　American　Chemical　Society.