One　of　the　most　important　phenomena　in　developing　renewable　and　sustainable　energy　methods　is　electro-catalytic　water　splitting.　Higher　loadings　of　single　metal　atom　oxide　(SMAO)　(M:　W,　Cu,　and　Co)　in　Co3O4-rGO　catalysts　are　credited　with　boosting　their　efficiency　in　electrocatalytic　oxygen　evolution　reaction　(OER)　and　photodegradation　of　tetracycline　(TC).　In　this　work,　we　investigated　the　catalytic　activity　of　electrocatalysts　for　OER　by　preparing　ultrathin　Co3O4　nanosheets　and　reduced　graphene　oxide　(rGO)　embedded　with　SMAO　(rGO-ED-Co3O4-WCuCo-30)　using　a　simple　one-pot　sonication　process.　The　well-designed　rGO-ED-Co3O4-WCuCo-30　electrocatalyst　allows　for　the　delivery　of　current　densities　of　10　and　100　mA　cm-2　at　overpotentials　of　291　and　365　mV,　respectively,　with　a　relatively　modest　Tafel　slope　of　57.9　mV　dec-1　during　OER.　The　densely　embedded　SMAO　particles　on　the　Co3O4　surface　are　responsible　for　this　behavior　because　they　increase　the　electrochemical　surface　area　with　a　large　number　of　active　sites　in　a　synergistic　manner.　The　rGO-ED-Co3O4-WCuCo-30　catalyst　was　used　effectively　in　OER　with　outstanding　long-term　stability　for　more　than　24　h.　The　photocatalytic　results　further　show　that　the　activity　of　Co3O4　was　significantly　enhanced　by　the　addition　of　SMAO,　with　the　TC　degradation　efficiency　of　97.57%.