Maneuvering　precise　and　tunable　charge　transportation　has　remained　the　core　issue　of　photocatalysis,　but　meets　with　limited　success　owing　to　the　ultra-fast　charge　recombination　rate,　scarcity　of　applicable　co-catalysts,　and　difficulty　in　customizing　spatially　separated　carrier　transport　pathways.　Although　co-catalyst　engineering　affords　a　convenient　strategy　to　dominate　spatial　charge　migration　to　the　ideal　active　sites,　the　conventional　co-catalyst　modification　strategy　fails　to　exquisitely　mediate　the　interface　between　co-catalyst　and　semiconductor　matrix,　along　with　tedious　synthesis　procedures.　Herein,　an　insulating　polyelectrolyte　(NCP),　poly(diallyldimethylammonium　chloride),　is　uniformly　and　seamlessly　coated　on　the　transition　metal　chalcogenides　(TMCs)　substrates　via　a　facile　electrostatic　self-assembly　approach　and　strategically　serves　as　the　highly　efficient　catalytic　active　sites　for　stimulating　multifarious　photoredox　catalysis,　including　selective　organic　transformation　and　CO2　reduction.　The　crucial　roles　of　such　NCP　are　unambiguously　unraveled　via　comprehensive　experimental　and　theoretical　investigations,　which　include　increasing　reactant　adsorption,　providing　active　sites,　and　most　importantly,　boosting　interfacial　charge　transfer　rate.　The　electron-withdrawing　capability　of　NCP　fosters　the　effective　charge　separation　over　TMCs,　leading　to　the　concomitantly　improved　and　stable　photocatalytic　activities　toward　aromatic　nitro　compounds　reduction　and　CO2-to-syngas　conversion　under　visible　light.　Our　work　could　strengthen　our　fundamental　understanding　of　the　generic　unanticipated　charge　transport　characteristics　of　insulating　polymers　for　solar　energy　conversion.　©　2025　The　Author(s).　Advanced　Science　published　by　Wiley-VCH　GmbH.