Photocatalytic　conversion　of　CO2　to　high-value　products　plays　a　crucial　role　in　the　global　pursuit　of　carbon-neutral　economy.　Junction　photocatalysts,　such　as　the　isotype　heterojunctions,　offer　an　ideal　paradigm　to　navigate　the　photocatalytic　CO2　reduction　reaction　(CRR).　Herein,　we　elucidate　the　behaviors　of　isotype　heterojunctions　toward　photocatalytic　CRR　over　a　representative　photocatalyst,　g-C3N4.　Impressively,　the　isotype　heterojunctions　possess　a　significantly　higher　efficiency　for　the　spatial　separation　and　transfer　of　photogenerated　carriers　than　the　single　components.　Along　with　the　intrinsically　outstanding　stability,　the　isotype　heterojunctions　exhibit　an　exceptional　and　stable　activity　toward　the　CO2　photoreduction　to　CO.　More　importantly,　by　combining　quantitative　in　situ　technique　with　the　first-principles　modeling,　we　elucidate　that　the　enhanced　photoinduced　charge　dynamics　promotes　the　production　of　key　intermediates　and　thus　the　whole　reaction　kinetics.