In　this　work,　we　report　the　fabrication　of　polypyrrole/g-C　3　N　4　(PPy/g-C　3　N　4　)　nanocomposites　via　simple　wet-chemical　method.　The　photocatalytic　activities　of　the　composites　are　evaluated　for　water　splitting　to　evolve　H　2　,　Rhodamine　B　dye　(RhB)　and　2,4-dichlorophenol　(2,4-DCP)　degradation　under　visible-light.　The　results　reveal　that　the　photocatalytic　performance　of　g-C　3　N　4　for　H　2　evolution,　RhB　dye　and　2,　4-DCP　degradation　are　significantly　improved　after　coupling　polypyrrole　(PPy).　Worth　noting,　the　amount　optimized　(1　wt%PPy/g-C　3　N　4　)　photocatalyst　showed　highest　photoactivity　compared　to　the　other　photocatalysts.　Further,　it　is　confirmed　by　means　of　radical　trapping　experiments　that　superoxide　radical　(O　2　[rad]　−　)　is　the　dominant　specie　involved　in　the　degradation　of　pollutants　over　PPy/g-C　3　N　4　nano-composites.　Moreover,　clear　photocatalytic　reactions　for　H　2　evolution　and　pollutants　degradation　are　proposed.　This　work　would　help　us　to　deeply　understand　the　reaction　mechanism　and　will　provide　feasible　routes　to　fabricate　g-C　3　N　4　based　highly　efficient　photocatalysts　for　energy　and　environmental　applications.　©　2019　Elsevier　B.V.