Ultrasound-assisted decoration of CuOx nanoclusters on TiO2 nanoparticles for additives free photocatalytic hydrogen production and biomass valorization by selective oxidation

Abstract

• Ultrasound-assisted ultra-wet (US-UWet) impregnation synthetic method is presented. • Mixed cupric and cuprous oxides nanoclusters (< 4 nm) were decorated on TiO 2 P25. • The nanocomposite showed H 2 formation capability under low power UV irradiation. • The additive free oxidation of biomass derived model platform chemicals was studied. • Nanocomposite revealed higher selectivity comparing to P25 for HMF and BnOH oxidation. The herein presented ultrasound-assisted ultra-wet (US-UWet) impregnation synthetic approach was followed in order to avoid the drawbacks of the conventional wet impregnation synthesis. The goal was to homogeneously decorate the surface of the TiO 2 nanoparticles with nanometric sized (< 4 nm) clusters of mixed cupric and cuprous oxides. The physicochemical features of the nanocomposite (TiO 2 CuO x ) were determined by high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and Diffuse reflectance (DR) spectroscopy. TiO 2 CuO x showed an enhanced and continuous capability to generate molecular hydrogen upon low power ultraviolet irradiation. The benchmark commercial TiO 2 P25 did not reveal any H 2 formation under these conditions. TiO 2 CuO x presented also a high efficiency for the additives-free selective partial oxidation of two well established biomass derived model platform chemicals/building blocks, 5-hydroxymethylfurfural (HMF) and benzyl alcohol (BnOH) to the value-added chemicals 2,5-diformylfuran (DFF) and benzyl aldehyde (PhCHO), respectively. The nanocomposite showed higher DFF and PhCHO yield compared to P25.