(629b) Hydrogen Production Via Photocatalytic Water Splitting over Mesoporous Pt/TiO2

Mesoporous TiO₂ semiconductors were synthesized by sol-gel technique, using a triblock-copolymer-templating, named Pluronic F-127. In order to minimize the electron-hole pair recombination, Pt was added as an electron trap in different percentages (i.e. 1.00 wt. %, 2.50 wt. %) during the sol-gel synthesis of the TiO₂ semiconductors. This was followed by calcination at 500 ^oC and 550 ^oC. Semiconductors' activity was evaluated in a bench-scale Photo-CREC-Water II (PCWII) photoreactor. In this sense, water splitting was carried out under near-UV light for hydrogen molecule production in the PCWII Reactor using ethanol at 2 % v/v as a renewable organic scavenger (electron donor). Ethanol acts as a good hole scavenger. The PCWII consisted of a 2.65 L internally irradiated slurry annular reactor with a 15 W T8 Black-Light-Blue (F15T8/BLB) lamp. The optimal photocatalyst loading was 0.15 g L^-1 in acid medium (pH = 4.0). The volume of the aqueous suspension was 6.0 L. Thereby the present study shows that mesoporous TiO₂ with 2.50 wt. % of Pt exhibits the best activity for hydrogen production under the same photoreaction conditions. This semiconductor material showed: a) An anatase phase with XRD, b) A reduced band gap at 2.34 eV was calculated, employing UV-Vis spectroscopy and a Tauc plot, c) 10-30 nm TiO₂ particles with SEM-EDX, d) A 140 m²/g BET surface area as well as 10 nm and 20 nm bimodal pore size distributions. Furthermore, the absorbed photons on the photocatalysts have been studied by employing macroscopic balances. These macroscopic energy balances considered for incident, scattered and transmitted near-UV photons. In this respect, evaluated Quantum Yields (QY) displayed a promising 0.27 (27%) when utilizing mesoporous 2.50 wt. % Pt/TiO₂-550^oC.