Tuning Thiophene‐Based Phenothiazines for Stable Photocatalytic Hydrogen Production

Dibranched donor–(π–acceptor) 2 dyes, where phenothiazine is the donor core, cyanoacrylic acid is the acceptor/anchoring group, and π is represented by mono‐ and poly‐cyclic simple and fused thiophene derivatives, were tested as photosensitizers in the photocatalytic production of H 2 , in combination with a Pt/TiO 2 catalyst. The optical and electrochemical properties of the dyes were investigated, showing that careful design of the thiophene‐based π spacer afforded enhanced optical properties. In the H 2 production over 20 h, the new thiophene‐based sensitizers revealed improved stability after longer irradiation times and enhanced performances, in terms of H 2 production rates and light‐to‐fuel efficiencies, after an initial activation period, which were for the first time associated with enhanced stability under photocatalytic production of H 2 and the absence of critical dye degradation.