Effect of donor-donor-π-acceptor architecture of triphenylamine-based organic sensitizers over TiO2 photocatalysts for visible-light-driven hydrogen production

In this paper, we report a series of triphenylamine (TPA) donor based dyes in sensitized hydrogen production over TiO2-Pt catalysts under visible light. Among the selected dyes, 4-(diphenylamino) phenylcyanoacrylic acid (DN-F01), 5-[4-(diphenylamino)phenyllthiophene-2-cyanoacrylic acid (DN-F02), 3-(5-(4-(diphenylamino)styryl) thiophen-2-y1)-2-cyanoacrylic acid (DN-F03), (E)-3-(5-(4-(bis(2',4'-dibutoxy-[1,1'-biphenyl]-4-yl)amino) phenyl) thiophen-2-y1)-2-cyanoacrylic acid (DN-F04) and 3-(6-(4-(bis(2',4'-dibutoxy-[1,1'-bipheny1]-4-yl)amino)pheny1)-4,4-dihexyl-4H-cyclopenta[1,2-b:5,4-b'] dithiophen-2-y1)-2-cyanoacrylic acid (DN-F05) were adsorbed on Pt-TiO2 and tested for photocatalytic hydrogen production under visible-light in presence of triethanolamine (TEOA) as sacrificial electron donor (SED). The enhanced light absorption and effective interfacial charge transfer from excited dye to TiO2 is significant in DN-F05-TiO2. The DN-F05 sensitized Pt -TiO2 (DNS@T) photocatalyst exhibited higher turnover number (TON 1864) and apparent quantum efficiency (AQE similar to 44%) when compared to their corresponding simple architecture dye molecules. Moreover, the additional donating group di-butoxyphenyl and dihexyl-cyclopentyl pi-conjugated bridge units provide an excellent surface protection through steric hindrance leading to a good photocatalytic performance. Electrochemical and computational studies suggest the better photocatalytic activity of DNS@T. The photocatalyst shows long term stability and reproducibility at neutral pH. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.