Au/CeO2 Photocatalyst for the Selective Oxidation of Aromatic Alcohols in Water under UV, Visible and Solar Irradiation

Elisa I García-López,Zahra Abbasi,Giuseppe Marcì,Francesco Parrino,Valeria La Parola,Leonarda F Liotta

doi:10.3390/catal11121467

Abstract

Au nanoparticles supported on CeO2 have been prepared and investigated as photocatalysts for the photocatalytic selective oxidation of benzyl alcohol and 4-methoxybenzyl alcohol to the correspondent benzaldehydes, in aqueous suspensions and room conditions under UV, visible and natural solar light irradiation. Au nanoparticles have been supported by impregnation (1 and 3 wt.%) on two types of CeO2 (i.e., a commercial one and a home prepared oxide obtained in the presence of NaOH as precipitation agent). The Au impregnated samples showed strong visible radiation absorption at 565–570 nm associated to localized surface plasmon resonance (LSPR). The bare CeO2 samples are activated by UV light and resulted virtually inactive under visible irradiation, whereas the presence of Au improved both the conversion of the alcohols and the selectivity of the reaction towards the aldehyde, giving rise to good results, particularly under visible and natural solar light irradiation. The activity of the materials increased by increasing the Au content.

Highlights

The development of green and sustainable technologies is a big challenge of the current scientific research in applied sciences
No gold signals are visible in the X-ray diffraction patterns (XRD) patterns of both Au1% catalysts, while slightly detectable features were observed in the case of the Au3% catalysts, corresponding to an average size of ca. 3.5 and ca. 2.5 nm, in the case of the CeO2 Aldrich and the hp supported samples, respectively
No go signals are visible in the XRD patterns of both Au1% catalysts, while slightly detectab features were observed in the case of the Au3% catalysts, corresponding to an averag size of ca. 3.5 and ca. 2.5 nm, in the case of the CeO2 Aldrich and the hp supported sample respectively

Summary

Introduction

The development of green and sustainable technologies is a big challenge of the current scientific research in applied sciences. The use of solar energy as clean and renewable energy source is a priority for the technologies aiming to develop photocatalytic transformations where the energy of photons can be used to drive many useful chemical reactions, including solar production of fuels, water purification and selective reactions. The generation of electron/hole couples is responsible of oxidation and reduction processes. The photogenerated electrons reduce the adsorbed oxygen (O2), if the process is carried out in air, to form superoxide radicals (O2−) and the photogenerated holes react with H2O to form hydroxyl radicals (OH), generally responsible for the oxidation of substrates resulting in their mineralization and/or partial oxidation [1]. Photocatalysis is a promising technology for selective oxidation, alternative to traditional chemical methods based on reactions that are usually carried out at high temperatures and pressure with hazardous and harmful reagents. Photocatalysts responsive to visible light are interesting, mostly those active under natural sunlight as the energy source

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Conclusion