High‐Efficiency and Stability Phenothiazine‐Based D–(A′–π–A) ₂ Sensitized Photocatalytic Hydrogen Evolution Under Visible Light

Three novel phenothiazine (PTZ)‐based photocatalysts were rationally designed and integrated with Pt@TiO 2 for photocatalytic hydrogen evolution. PTZ‐1 adopts a D–(π–A) 2 architecture, whereas PTZ‐2 and PTZ‐3 feature D–(A′–π–A) 2 configurations incorporating benzothiadiazole (BTD) and isoindigo as auxiliary acceptors, respectively. All photocatalysts were immobilized on Pt@TiO 2 through dianchoring groups to ensure efficient interfacial charge transfer. In particular, PTZ‐2 —incorporating benzothiadiazole as an auxiliary electron acceptor—exhibited the highest photocatalytic activity, delivering a high turnover number (TON) and turnover frequency (TOF) of 10,714.2 and 691.2 (after 15.5 h), respectively, with total hydrogen evolution of 92,534 μmol g −1 after 15.5 h and 264,646 μmol g −1 after 60 h at a dye loading of 17.9 μmol g −1 . This superior performance is primarily attributed to favorable energy‐level alignment and enhanced electron‐injection efficiency imparted by the BTD unit. Notably, PTZ‐2 displays the longest electron lifetime (0.62 ns) and the lowest charge–transfer resistance, indicating efficient charge separation and suppressed recombination. Furthermore, PTZ‐2 retained 97% of its initial hydrogen‐evolution activity after 60 h under identical conditions, demonstrating excellent long‐term stability under visible light.