Developing　bifunctional　electrocatalysts　with　abundant　reserves　and　efficient　performance　is　significant　for　alkaline　water　electrolysis.　Herein,　the　antiperovskite　nitride　(FexCu1-x)4N　particles　anchored　on　the　surface　of　Cu2O　nanosheets　have　been　synthesized　by　one-step　solution　combustion　synthesis　with　the　assistance　of　KCl.　The　(FexCu1-x)4N　interacts　with　Cu2O　in　the　form　of　p-n　junction.　Such　an　assembly　effectively　promotes　the　charge　transfer　under　the　interval　built-in　field,　which　can　regulate　the　electronic　densities　to　greatly　increase　the　reaction　kinetics　and　available　active　sites.　Moreover,　the　electrocatalysts　experience　the　different　structural　evolution　during　HER　and　OER　process.　The　in-situ　reconstructed　species　possess　a　proper　free　energy　of　adsorbed　intermediates　for　highly　efficient　bifunctional　electrocatalysis　via　DFT　calculation.　The　optimal　(Fe1xCux)4N-Cu2O　heterostructure　couples　show　a　superior　bifunctional　performance　for　water　electrolysis,　with　a　low　cell　voltage　of　1.57　V　at　10　mA　cm-2　and　nearly　100　%　Faraday　efficiency,　surpassing　the　benchmark　precious　metal　couples.