Photocatalytic H<SUB align="right">2 production from ethanol over Au/TiO<SUB align="right">2 and Ag/TiO<SUB align="right">2

Abstract

This paper compares the photocatalytic activities of Au/TiO 2 (Au loadings 0–4 wt.%) and Ag/TiO 2 photocatalysts (Ag loadings 0–4 wt.%) for H 2 production from ethanol-water mixtures under UV irradiation. Au and Ag nanoparticles were deposited on commercially available Degussa P25 TiO 2 (85% anatase, 15% rutile) using deposition-precipitation and liquid impregnation methods, respectively. TEM analyses showed the average noble metal nanoparticle size to be ~5 nm for the Au/TiO 2 photocatalysts and ~3 nm for the Ag/TiO 2 photocatalysts. Au/TiO 2 photocatalysts showed a strong localised surface plasmon resonance (LSPR) at 570 nm characteristic for nanocrystalline Au. Complementary XRD studies confirmed that Au and Ag nanoparticles were present in metallic form. Photoluminescence measurements revealed that Au and Ag nanoparticles effectively suppress electron-hole recombination in TiO 2 , thereby enhancing the photocatalytic activity of TiO 2 for hydrogen production. Au/TiO 2 photocatalysts were far more active for H 2 production from ethanol-water mixtures than Ag/TiO 2 photocatalysts. A 1 wt.% Au/TiO 2 photocatalyst yielded the highest H 2 production rate (34 mmol g –1 h –1 ). Amongst the Ag/TiO 2 photocatalysts, the 2 wt.% Ag/TiO 2 sample was the most active (3.7 mmol g –1 h –1 ). Results are rationalised in terms of differences in the electronic properties of supported Au and Ag nanoparticles, with the former being near ideal for H 2 production.