A　series　of　novel　composites　g-C3N4/SnO2　were　first　synthesized　using　a　facile　two-step　process.　Through　systematic　sample　characterization,　it　is　demonstrated　that　all　composites　consist　of　two　components:　g-C3N4　with　a　low　specific　surface　area　and　SnO2　nanoparticles　with　a　large　specific　surface　area.　Within　the　composites,　component　of　SnO2　nanoparticles　dispersed　well　onto　the　component　g-C3N4　with　a　clear　interface　between　each　other.　The　interactions　between　both　components　are　strong,　as　confirmed　by　variations　in　binding　energies　and　lattice　parameters.　A　synergistic　collaboration　is　achieved　for　the　composites,　as　contributed　by　surface　adsorption　of　organics　from　π-π　conjugation　of　component　g-C3N4,　improved　separation　efficiency　of　photo-generated　carriers　from　interfacial　interactions　between　both　components,　and　increased　surface　area　from　component　SnO2　nanoparticles.　As　a　consequence,　these　composites　exhibit　a　significantly　enhanced　photocatalytic　activity　towards　MO　degradation　under　visible　light　irradiation.　The　optimum　photocatalytic　performance　is　achieved　at　47.5wt%　SnO2,　showing　a　reaction　kinetic　constant　of　0.0078,　which　is　much　higher　than　those　of　components　g-C3N4　and　SnO2.　With　the　unique　synergistic　collaboration,　the　optimized　composite　with　Pt　additives　is　also　successfully　applied　to　high-efficiency　production　of　hydrogen　from　water　splitting　under　visible　light　irradiation.　©　2014　Elsevier　B.V.