Solar　hydrogen　production　at　a　high　efficiency　holds　the　significant　importance　in　the　age　of　energy　crisis,　while　the　micro-environment　manipulation　of　active　sites　on　photocatalysts　plays　a　profound　role　in　enhancing　the　catalytic　performance.　In　this　work,　a　series　of　well-defined　single-site　Ni-grafted　TiO2　photocatalysts　with　unique　and　specific　coordination　environments,　2,2′-bipyridine-Ni−O−TiO2　(T−Ni　Bpy)　and　2-Phenylpyridine-Ni−O−TiO2　(T−Ni　Phpy),　were　constructed　with　the　methods　of　surface　organometallic　chemistry　combined　with　surface　ligand　exchange　for　visible-light-induced　photocatalytic　hydrogen　evolution　reaction　(HER).　A　prominent　rate　of　33.82　μmol　⋅　g−1　⋅　h−1　and　a　turnover　frequency　of　0.451　h−1　for　Ni　are　achieved　over　the　optimal　catalyst　T−Ni　Bpy　for　HER,　260-fold　higher　than　those　of　Ni−O−TiO2.　Fewer　electrons　trapped　oxygen　vacancies　and　a　larger　portion　of　long-lived　photogenerated　electrons　(＞3　ns,　~52.9　%),　which　were　demonstrated　by　the　electron　paramagnetic　resonance　and　femtosecond　transient　IR　absorption,　correspond　to　the　photocatalytic　HER　activity　over　the　T−Ni　Bpy.　The　number　of　long-lived　free　electrons　injected　from　the　Ni　photoabsorber　to　the　conduction　band　of　TiO2　is　one　of　the　determining　factors　for　achieving　the　excellent　HER　activity.　©　2023　Wiley-VCH　GmbH.