Disclosing　the　roles　of　reactive　sites　at　catalytic　interfaces　is　of　paramount　importance　for　understanding　the　reaction　mechanism.　However,　due　to　the　difficulties　in　the　detection　of　reaction　intermediates　in　the　complex　heterophase　reaction　system,　disentangling　the　highly　convolved　roles　of　different　surface　atoms　remains　challenging.　Herein,　we　used　CoOx　as　a　model　catalyst　to　study　the　synergy　of　CoTd2+　and　CoOh3+　active　sites　in　the　electrocatalytic　oxygen　evolution　reaction　(OER).　The　formation　and　evolution　of　reaction　intermediates　on　the　catalyst　surface　during　the　OER　process　were　investigated　by　in　situ　surface-enhanced　Raman　spectroscopy　(SERS).　According　to　the　SERS　results　in　ion-substitution　experiments,　CoOh3+　is　the　catalytic　site　for　the　conversion　of　OH-　to　O-O-　intermediate　species　(1140-1180　cm-1).　CoOOH　(503　cm-1)　and　CoO2　(560　cm-1)　active　centers　generated　during　the　OER,　at　the　original　CoTd2+　sites　of　CoOx,　eventually　serve　as　the　O2　release　sites　(conversion　of　O-O-　intermediate　to　O2).　The　mechanism　was　further　confirmed　on　Co2+-Co3+　layered　double　hydroxides　(LDHs),　where　an　optimal　ratio　of　1:1.2　(Co2+/Co3+)　is　required　to　balance　O-O-　generation　and　O2　release.　This　work　highlights　the　synergistic　role　of　metal　atoms　at　different　valence　statuses　in　water　oxidation　and　sheds　light　on　surface　component　engineering　for　the　rational　design　of　high-performance　heterogeneous　catalysts.　©　2022　American　Chemical　Society.