Shedding light on small molecule coumarin dyes for efficient photocatalytic hydrogen evolution.

The development of simple coumarin-based organic dyes loaded over TiO 2 is found to possess great potential for efficient photocatalytic hydrogen generation. Herein, we studied a series of coumarin-based organic dyes, namely, 4-(naphthalene-1-yl)-2-oxo-2H-benzo[h]chromene-3-carbonitrile loaded over Pt–TiO 2 is referred to as TC-2. The electronic as well as structural properties of the dyes were visualized experimentally and theoretically with the modification of the structural chromophoric groups over the meso-position of the coumarin dyes and revealed that the meso-substitution of the naphthalene ring over the TC-2 resulted in the decrease in electron-hole recombination dynamics. TC-2 photocatalyst depicted enhanced activity of (H 2 rate-5.54 mmolg−1h−1) under neutral pH (AQY-14.5%, TON-5970), which is majorly obtained due to the increased conjugation of the naphthalene ring which thereby increases the light-sorption capacity of the materials in comparison to that of the others, synthesized materials in presence of TEOA. The extended π-π∗ conjugation in the substituent modification and the cyano groups over the simple coumarin groups leads to enhanced activity. This work paves the way towards sustainable development of dye-sensitized photocatalysts for green fuel generation. • Small molecule coumarin dyes were reported in photocatalytic H 2 generation. • The effect of substituent, cyano-functional group on HER has been investigated. • Dye-TiO 2 (TC-2) exhibited H 2 rate 5.54 mmol.g−1h−1 under neutral pH (AQY-14.5%, TON-5970). • The lifetime decay study revealed long lifetime of the TC-2, with 7.73 ns established superior HER. • DFT studies reveal better overlap and charge separation in photocatalyst. [ABSTRACT FROM AUTHOR]