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

Abstract

Pt/TiO2 (Pt loadings 0-4 wt%) and Au/TiO2 (Au loadings 0-4 wt%) photocatalysts were synthesized, char- acterized and tested for H2 production from ethanol-water mixtures (80 vol% ethanol, 20 vol% H2O) under UV exci- tation. 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 *570 nm, typical for metallic Au nanoparticles of diameter *5 nm supported on TiO2. X-ray photoelectron spectros- copy 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 phot- ocatalysts both displayed very high activities for H2 pro- duction under UV irradiation, with the Au/TiO2 samples affording slightly superior rates of H2 production at most metal loadings. The 2 wt% Au/TiO2 and 1 wt% Pt/TiO2 photocatalysts showed the highest H2 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 H2 production by acting as electron acceptors and thereby suppressing electron-hole pair recombination in TiO2.