Abstract
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•Preparation of stable monodispersed copper clusters protected by N-acetyl-L-cysteine.•The charge state of copper clusters is zero as confirmed by XPS.•Cu@NALC/TiO2/AC nanocomposite shows the highest efficient photocatalytic activity and recyclability.•The prepared nanocomposites show 100 % selectivity benzaldehyde product.•Cheap and novel nanocomposites were used as a photocatalysts in solar oxidation of BA.
Great efforts have been made to enhance the efficiency of the solar light-activated photocatalyst in recent years. In this work, monodispersed copper nanoclusters protected by N-acetyl-L-cysteine ligand (Cu@NALC) were synthesized. The optical properties and chemical composition of the synthesized copper clusters were studied by UV-vis and FTIR spectroscopies, and thermogravimetric analysis (TGA), respectively. The charge of copper atoms in Cu@NALC clusters was zero as was confirmed by X-ray photoelectron spectroscopy (XPS). A novel nanocomposite consisting of ∼1 nm copper clusters, Degussa TiO2 P25, and activated carbon (Cu@NALC/TiO2/AC) was prepared to use as a solar light-activated photocatalyst. The synthesized copper clusters showed significantly increase solar light absorption and improved the efficiency of Cu@NALC/TiO2/AC nanocomposite for photocatalytic oxidation of benzyl alcohol (BA), compared with Cu@NALC/AC and TiO2/AC nanocomposites. Cu@NALC clusters induce the TiO2 to absorb the visible light, where the copper nanoclusters absorb visible light from 400-700 nm. The copper clusters mainly adsorb on the surface of TiO2 nanoparticles, as well on the activated carbon surface as shown in HR-TEM analysis. The highly efficient photocatalytic activity of this nanocomposite is attributed also to the large surface area of activated carbon as shown in surface area analysis (692.8 m2/g). Cu@NALC/TiO2/AC nanocomposite achieved 100% conversion of BA with ≥99 % selectivity after 6 h solar irradiation; however Cu@NALC/AC, TiO2/AC and TiO2-P25 showed only 66.35 %, 55.43 % and 44.78 %, respectively. All the components of this nanocomposite are cheap and available, in addition to the high photocatalytic activity, were found to be the most economically and suitable system for the industrial application.