Modulating　the　electronic　structure　of　an　electrocatalyst　via　interface　engineering　is　a　promising　strategy　to　accelerate　the　overall　electrocatalytic　water　splitting.　In　this　work,　a　novel　three-phase　heterojunction　Fe2P–CoP/CeO2　is　constructed　via　interface　engineering　combined　with　a　selective　phosphorization　process.　Coupling　CeO2　at　the　interface　of　Fe2P　and　CoP　effectively　promotes　the　redistribution　of　electrons　at　the　three-phase　interface,　which　optimizes　the　Gibbs　free　energy　of　H*　adsorption　energy　and　significantly　reduces　the　water　dissociation　energies,　thus　boosting　the　electrocatalytic　water　splitting　in　alkaline　media.　As　a　result,　the　Fe2P–CoP/CeO2-20　exhibits　excellent　performances　toward　HER　(η10=45　mV,　η50=　100　mV)　and　OER　(η10=248　mV,　η50=　278　mV).　Moreover,　an　overall　water　splitting　electrolyzer　constructed　by　Fe2P–CoP/CeO2-20　only　requires　a　cell　voltage　of　1.52　V　to　deliver　a　current　density　of　10　mA　cm−2.　Interestingly,　the　assembled　electrolyzer　can　also　be　driven　by　a　solar　panel　for　overall　water　splitting.　This　work　offers　a　feasible　strategy　for　regulating　the　electronic　structure　of　three-phase　heterojunction　interface　to　promote　electrochemical　water　splitting.　©　2022　Elsevier　B.V.