Photocatalysts for H2 Generation from Starburst Triphenylamine/Carbazole Donor‐Based Metal‐Free Dyes and Porous Anatase TiO2 Cube

A series of novel triphenylamine/carbazole-based D-D-π-π-A dyes DH1-4 and a mesoporous anatase cubic "microcage" TiO2 material (denoted as MC-TiO2 ) were synthesized and combined to obtain dye-sensitized photocatalysts (denoted as DHn/Pt/MC-TiO2 , n=1-4). These catalysts showed better performances in visible-light-driven H2 evolution from water than DHn/Pt/P25-TiO2 catalysts based on commercial P25-TiO2 bulk semiconductor under similar conditions. Compared with P25-TiO2 particles, the porous MC-TiO2 had a large Brunauer-Emmett-Teller surface area, porosity, and exposed {0 0 1} crystal plane, which greatly contributed to the photocatalytic activity. The optimized DH2/Pt/MC-TiO2 photocatalyst exhibited an attractive H2 production rate (16.28 mmol g-1 h-1 based on catalyst mass), and the optimized DH4/Pt/MC-TiO2 photocatalyst showed good stability [turnover number (TON) of 16 699 in 105 h based on dye number], which represents one of the best performances among all reported visible-light-driven heterogeneous catalytic systems. Compared with the other dyes in this series, the high H2 production rate of DH2 on Pt/MC-TiO2 can be attributed to its size-matching effect and thus high dye loading amount, whereas the high TON and durability of DH4/Pt/MC-TiO2 are probably related to the rapid regeneration kinetics of DH4.