Semiconductor-based　photocatalysis　has　been　considered　as　one　of　the　most　effective　techniques　to　achieve　the　conversion　of　clean　and　sustainable　sunlight　to　solar　fuel,　in　which　the　construction　of　novel　solar-driven　photocatalytic　systems　is　the　key　point.　Here,　we　report　initially　the　synthesis　of　modified　graphitic　carbon　nitride　(g-C　3　N　4　)　nanorods　via　the　calcination　of　intermediates　obtained　from　the　co-polymerization　of　precursors,　and　the　in-situ　hybridization　of　Ag　3　PO　4　with　as-prepared　modified　g-C　3　N　4　to　produce　g-C　3　N　4　nanorod/Ag　3　PO　4　composite　materials.　The　diameter　of　modified　rod-like　g-C　3　N　4　materials　is　determined　to　be　around　1　μm.　Subsequently　the　morphological　features,　crystal　and　chemical　structures　of　the　assembled　g-C　3　N　4　nanorod/Ag　3　PO　4　composites　were　systematically　investigated　by　SEM,　XRD,　XPS,　UV–vis　diffuse　reflectance　spectra　(DRS).　Furthermore,　the　use　of　as-prepared　composite　materials　as　the　catalyst　for　photocatalytic　oxygen　evolution　from　water　splitting　was　studied.　The　oxygen-generating　results　showed　that　the　composite　photocatalyst　modified　with　600　mg　rod-like　g-C　3　N　4　demonstrates　2.5　times　higher　efficiency　than　that　of　bulk　Ag　3　PO　4　.　The　mechanism　behind　the　enhancement　in　the　oxygen-evolving　activity　is　proposed　on　the　basis　of　in-situ　electron　spin　resonance　(ESR)　measurement　as　well　as　theoretical　analysis.　The　study　provides　new　insights　into　the　design　and　development　of　new　photocatalytic　composite　materials　for　energy　and　environmental　applications.　©　2017　Elsevier　B.V.