Solar-driven　water　splitting　over　semiconductor-based　photocatalysts　provides　direct　conversion　of　solar　energy　to　chemical　energy,　in　which　electron-hole　separation　and　charge　transport　are　critical　for　enhancing　the　photocatalytic　activity　of　semiconducting　materials.　Moreover,　the　search　for　active　photocatalysts　that　efficiently　oxidize　water　remains　a　challenging　task.　Here,　we　demonstrate　that　a　series　of　Ag3PO4/Ag/graphene/graphitic　carbon　nitride　(g-C3N4)　heterostructured　materials　can　drive　photocatalytic　water　oxidation　efficiently　under　LED　illumination.　The　water　oxidation　behavior　of　as-prepared　composite　photocatalysts　in　relation　to　the　added　amount　of　g-C3N4　and　the　roles　of　electron　mediators　was　investigated　in　detail.　Based　on　the　illuminated　Z-scheme　photocatalytic　mechanism,　the　photogenerated　electrons　and　holes　can　be　separated　effectively　and　the　electron-hole　recombination　of　bulk　material　is　suppressed.　The　reduced　metallic　Ag　nanoparticles　were　found　to　function　as　the　center　for　the　accumulation　of　electrons　from　Ag3PO4　and　holes　from　g-C3N4.　By　exploiting　the　proper　addition　of　g-C3N4　into　the　composite,　photocatalytic　oxygen　evolution　performance　over　the　heterostructured　materials　could　be　suitably　tuned,　which　resulted　in　highly　efficient　water　oxidation.　©　2017　Elsevier　B.V.