Title: Photocatalytic H₂ production from ethanol over Au/TiO₂ and Ag/TiO₂

Authors: Vedran Jovic; Pei-Huan Hsieh; Wan-Ting Chen; Dongxiao Sun-Waterhouse; Tilo Söhnel; Geoffrey I.N. Waterhouse

Addresses: School of Chemical Sciences, The University of Auckland, 23 Symonds Street, Auckland 1142, New Zealand ' School of Chemical Sciences, The University of Auckland, 23 Symonds Street, Auckland 1142, New Zealand ' School of Chemical Sciences, The University of Auckland, 23 Symonds Street, Auckland 1142, New Zealand ' School of Chemical Sciences, The University of Auckland, 23 Symonds Street, Auckland 1142, New Zealand ' School of Chemical Sciences, The University of Auckland, 23 Symonds Street, Auckland 1142, New Zealand ' School of Chemical Sciences, The University of Auckland, 23 Symonds Street, Auckland 1142, New Zealand

Abstract: This paper compares the photocatalytic activities of Au/TiO₂ (Au loadings 0-4 wt.%) and Ag/TiO₂ photocatalysts (Ag loadings 0-4 wt.%) for H₂ production from ethanol-water mixtures under UV irradiation. Au and Ag nanoparticles were deposited on commercially available Degussa P25 TiO₂ (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/TiO₂ photocatalysts and ~3 nm for the Ag/TiO₂ photocatalysts. Au/TiO₂ 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 TiO₂, thereby enhancing the photocatalytic activity of TiO₂ for hydrogen production. Au/TiO₂ photocatalysts were far more active for H₂ production from ethanol-water mixtures than Ag/TiO₂ photocatalysts. A 1 wt.% Au/TiO₂ photocatalyst yielded the highest H₂ production rate (34 mmol g⁻¹ h⁻¹). Amongst the Ag/TiO₂ photocatalysts, the 2 wt.% Ag/TiO₂ 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 H₂ production.

Keywords: photocatalysis; ethanol; titania; gold; silver; hydrogen production; sustainability; renewable energy; nanotechnology; photoluminescence; nanoparticles; electronic properties; sustainable development.

DOI: 10.1504/IJNT.2014.060591

International Journal of Nanotechnology, 2014 Vol.11 No.5/6/7/8, pp.686 - 694

Published online: 16 Dec 2014 *

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