Tuning Thiophene-Based Phenothiazines for Stable Photocatalytic Hydrogen Production

Dibranched donor-(pi-acceptor) 2 dyes, where phenothiazine is the donor core, cyanoacrylic acid is the acceptor/anchoring group, and pi 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/TiO2 catalyst. The optical and electrochemical properties of the dyes were investigated, showing that careful design of the thiophene-based pi 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.