Carrier　spatial　separation　efficiency　and　active　electron　density　are　the　key　factors　affecting　photocatalytic　hydrogen　evolution　activity.　Heterojunction　catalysts　with　fast　charge　separation　and　directed　electron　transport　systems　were　successfully　prepared　by　a　synergistic　modification　strategy　of　transition　metal　(Co)　doping　and　crystal　plane　modulation.　The　optimized　electronic　structure　and　enhanced　reaction　kinetics　enabled　unidirectional　electron　transfer.　Photocatalytic　results　show　that　CdS(002)/Co-C3N4　exhibits　remarkable　hydrogen　evolution　activity　(991.2　μmol　h−1　g−1)　in　the　absence　of　a　co-catalyst,　which　is　37.0　and　3.4　times　higher　than　that　of　C3N4　(26.8　μmol　h−1　g−1)　and　Co-C3N4　(294.6　μmol　h−1　g−1),　respectively.　Density　functional　theory　(DFT)　calculations　indicate　that　the　enhanced　catalytic　activity　of　CdS(002)/Co-C3N4　is　attributed　to　the　reduced　electron-hole　recombination　rate　and　the　increased　electron　density　at　the　active　site.　This　work　provides　a　new　idea　for　the　design　of　photocatalysts　with　directed　charge　transport　channels　from　the　perspective　of　re-optimizing　heterojunctions.　©　2023　The　Royal　Society　of　Chemistry.