Water　electrolysis　for　efficiently　generating　hydrogen　is　a　key　chemistry　to　realize　the　hydrogen　economy.　Transition　metal　phosphides　(TMPs)　have　become　promising　catalysts　for　hydrogen　evolution　reaction　(HER)　and　oxygen　evolution　reaction　(OER)　under　alkaline　conditions.　But　their　widespread　application　is　still　limited　due　to　the　intermediates＇　adsorption/desorption　energy　to　be　improved　and　the　rare　analysis　of　activation.　Herein,　we　demonstrate　a　bifunctional　catalyst,　bimetallic　phosphide　(NixCoyP)　supported　by　Ni　foam　(NF),　towards　HER　and　OER.　X-ray　photoelectron　spectra　demonstrate　that　the　synergy　between　nickel　and　cobalt　regulates　the　electron　redistribution　around　active　sites,　which　optimizes　reaction　intermediates＇　adsorption/desorption　kinetics　on　active　sites.　Post-stability　analysis　further　reveals　the　surface　activation　phenomenon,　that　NixCoyP　can　transform　into　hydroxides　for　HER　and　oxyhydroxides　for　OER.　Such　behaviors　allow　the　surface　of　catalysts　to　form　new　heterostructures　with　reorganized　electronic　structures　to　sustain　the　low　voltage　of　water　electrolysis　and　excellent　stability.　Density　functional　theory　analysis　proves　that　the　NiCoP/M-OH　heterostructure　significantly　enhances　the　HER　properties　through　the　optimized　adsorption/desorption　capacities　for　H*　intermediates.　Remarkably,　this　catalyst　exhibits　an　outstanding　overall　water　electrolysis　performance.