In　consideration　of　application　prospect　of　non-noble　metallic　materials　catalysts,　the　study　of　exploring　more　highly　effective　electrocatalysts　has　been　focused　on　by　researchers.　Herein,　a　novel　strategy　is　employed　to　construct　a　heterojunction　consisting　of　metal　phosphide　NixFeyP　and　layered　double　hydroxide　(LDH)　with　graphene　oxide　(GO)　as　conductive　support.　By　adjusting　the　molar　ratio　of　Ni　to　Fe,　a　series　of　heterojunctions　with　mixed　valence　state　Fe　delta+/Fe3+　and　Ni　delta+/Ni2+　(delta　is　likely　close　to　0)　redox　couples　are　achieved　and　strong　synergistic　effects　towards　overall　water　splitting　performance　are　found.　The　optimized　catalyst　with　a　Ni/Fe　molar　ratio　of　0.72:0.33,　namely　Ni-0.7　Fe0.3P/LDH/GO,　delivers　ultra-low　overpotentials　for　hydrogen　evolution　reaction　(HER)　and　oxygen　evolution　reaction　(OER)　of　79　and　198　mV　at　the　current　density　of　10　mA.cm(-2),　respectively.　Furthermore,　for　overall　water-splitting　practical　application,　it　only　requires　1.526　V　at　10　mA.cm(-2)　with　robust　stability,　which　is　superior　to　most　reported　electrocatalysts.　Experimental　results　demonstrate　the　improved　electronic　conductivity,　enlarged　electrochemically　active　area　and　accelerated　kinetics　together　account　for　the　enhanced　performance.　This　work　supplies　new　prospects　for　the　promotion　and　application　of　such　heterojunction　electrocatalysts　in　overall　water　splitting.