Photocatalytic H2 Production from Ethanol-Water Mixtures Over Pt/TiO2 and Au/TiO2 Photocatalysts: A Comparative Study

Pt/TiO2 (Pt loadings 0-4 wt%) and Au/TiO2 (Au loadings 0-4 wt%) photocatalysts were synthesized, characterized and tested for H-2 production from ethanol-water mixtures (80 vol% ethanol, 20 vol% H2O) under UV excitation. Average metal nanoparticle sizes determined by TEM were 1-3 nm for Pt in the Pt/TiO2 photocatalysts and 5-7 nm for Au in the Au/TiO2 photocatalysts. Au/TiO2 showed an intense localized surface plasmon resonance feature at similar to 570 nm, typical for metallic Au nanoparticles of diameter similar to 5 nm supported on TiO2. X-ray photoelectron spectroscopy and X-ray diffraction analyses established that Pt and Au were present in metallic form on the TiO2 support. X-ray fluorescence revealed close accord between nominal and actual Pt and Au loadings. The Au/TiO2 and Pt/TiO2 photocatalysts both displayed very high activities for H-2 production under UV irradiation, with the Au/TiO2 samples affording slightly superior rates of H-2 production at most metal loadings. The 2 wt% Au/TiO2 and 1 wt% Pt/TiO2 photocatalysts showed the highest H-2 production rates (32-34 mmol g(-1) h(-1)). Photoluminescence studies confirmed that Pt and Au nanoparticles positively enhance the photocatalytic properties of P25 TiO2 for H-2 production by acting as electron acceptors and thereby suppressing electron-hole pair recombination in TiO2.