Controlling　the　structure　of　semiconductors　to　tailor　are　physicochemical　and　photoelectronic　structure　features.　Graphitic　carbon　nitride　has　triggered　a　new　impetus　in　the　field　of　photocatalysis.　However,　the　rapid　recombination　of　charge　carriers　limited　its　photocatalytic　activity.　Herein,　we　demonstrate　that　potassium　doped　and　nitrogen　defects　into　graphitic　carbon　nitride　(KCNx)　framework　are　favorable　for　visible　light　harvesting,　charge　separation　and　have　highly　efficient　photocatalytic　behavior　for　water　splitting.　It　exhibits　a　high　hydrogen　evolution　activity　of　59.9　mmol·g−1·h−1　(66.6　times　much　higher　than　that　of　pristine　g-C3N4),　and　remarkable　apparent　quantum　efficiency　of　57.17%　at　420　nm.　The　superior　photocatalytic　performance　of　the　KCNx　sample　was　attributed　to　the　less　recombination　rate　of　photogenerated　electron　and　hole,　and　enhanced　conductivity,　which　was　proven　by　photoelectrochemical　and　PL.　This　work　reveals　the　synergistic　mechanism　of　introducing　foreign　elements　and　defects　into　the　framework　of　graphitic　carbon　nitride　to　improve　its　photocatalytic　activity.　©　2022　Hydrogen　Energy　Publications　LLC