Iridium　oxide　is　considered　the　only　practical　catalyst　for　oxygen　evolution　reaction　(OER)　in　commercial　proton　exchange　membrane　(PEM)　electrolyzers.　However,　its　low　activity　and　high　cost　greatly　hinder　the　large-scale　development　of　PEM　electrolyzers　for　hydrogen　production.　Herein,　we　report　atomically　dispersed　Ir　atoms　incorporated　into　a　spinel　Co3O4lattice　as　an　acidic　OER　catalyst,　which　exhibits　excellent　activity　and　stability　for　water　oxidation.　The　catalyst　significantly　lowers　the　over-potential　down　to　226　mV　at　10　mA　cm-2　with　an　ultrahigh　turnover　frequency　value　of　3.15　s-1　(eta　=　300　mV),　3　orders　of　magnitude　higher　than　that　of　commercial　IrO2.　Meanwhile,　the　catalyst　shows　superior　corrosion　resistance　in　an　acidic　OER　condition,　reaching　a　lifespan　of　up　to　500　h　at　10　mA　cm-2.　First-principles　calculations　reveal　that　the　key　*OOH　intermediate　can　be　stabilized　by　the　lattice　oxygen　coordinated　to　the　Ir　active　site　via　hydrogen　bond　formation,　which　substantially　regulates　the　rate-limiting　step　and　lowers　the　activation　free　energy　of　the　OER　process.　This　work　demonstrates　a　strategy　for　improving　the　OER　activity　of　Ir-based　catalysts　and　provides　insights　into　the　regulation　of　the　reaction　mechanism.