A　photocatalyst　system　is　generally　comprises　a　catalyst　and　cocatalyst　to　achieve　light　absorption,　electron-hole　separation,　and　surface　reaction.　It　is　a　challenge　to　develop　a　single　photocatalyst　having　all　functions　so　as　to　lower　the　efficiency　loss.　Herein,　the　active　GaN4　site　is　integrated　into　a　polymeric　carbon　nitride　(CN)　photocatalyst　(GCN),　which　displays　an　excellent　H2　production　rate　of　9904 μmol　h-1　　g-1　.　It　is　162　and　3.3　times　higher　than　that　of　CN　with　the　absence　(61 μmol　h-1　　g-1　)　and　presence　(2981 μmol　h-1　　g-1　),　respectively,　of　1.0 wt　%　Pt.　Under　light　irradiation　the　electron　is　injected　and　stored　at　the　GaN4　site,　where　the　LUMO　locates.　The　HOMO　distributes　on　the　aromatic　ring　resulting　in　spatial　charge　separation.　Transient　photovoltage　discloses　the　electron-storage　capability　of　GCN.　The　negative　GaN4　promotes　proton　adsorption　in　the　excited　state.　The　positive　adsorption　energy　drives　H2　desorption　from　GaN4　after　passing　the　electron　to　the　proton.　This　work　opens　up　opportunities　for　exploring　a　novel　catalyst　for　H2　production.