Synthesis of TiO₂@WO₃/Au Nanocomposite Hollow Spheres with Controllable Size and High Visible-Light-Driven Photocatalytic Activity

Abstract

A new nanocomposite was reported as a good-performance photocatalyst, i.e., double-shelled, positively and negatively charged, nanostructured hollow spheres with supported Au nanoparticles (NPs). TiO2, WO3, and Au NPs were coated successively onto the functionalized polystyrene (PS) template spheres. The as-synthesized product PS@TiO2@WO3/Au nanocomposites were calcined at elevated temperature and then intact double-shelled TiO2@WO3/Au hollow spheres were obtained. The dispersity, morphology, size, and lattice of TiO2@WO3/Au hollow spheres were investigated by SEM and TEM. The presence of TiO2 hollow sphere and WO3/Au shell was proved by HAADF-STEM and XRD images. The photodegradation activity for rhodamine B and trimesic acid (i.e., color and colorless aromatic pollutants) in decreasing order were TiO2@WO3/Au, TiO2–WO3, P25. Under visible-light irradiation, the photodegradation rate of rhodamine B and trimesic acid for TiO2@WO3/Au was 94% and 95%, respectively, which exhibited a significant increase of 62% and 80% as compared with P25. The synergistic effect of coupling TiO2 hollow spheres with WO3 shell and Au NPs on photocatalytic performance was proved by this article. First, Au NPs deposited in WO3 shell and loaded on TiO2 shell separately act as electron trap site and surface plasmon resonance-sensitizer, respectively, and hence the photogenerated electron–hole separation rate was improved. Second, the visible-light absorption of TiO2 hollow spheres was increased by the coexistence of WO3 and Au and unique hierarchical mesoporous architectures of TiO2@WO3/Au. Finally, the surface charge of TiO2@WO3/Au and rhodamine B was negative and positive, respectively, the affinity between them could be improved by electrical attractions, and then the major bottleneck in heterogeneous photocatalysis (i.e., poor affinity between pollutants and photocatalyst) could be broken. The optimal hollow sphere size of TiO2@WO3/Au was 450 nm, which was proved by the photodegradation of aromatic pollutants and photoreduction of Cr­(VI).

Electrochemical Synthesis of Nanostructured Metal-Doped Titanates and Investigation of Their Activity as Oxygen Evolution Photoanodes

“…Common avenues explored in attempts to extend the visible light absorption properties of the oxides to harness greater portions of the solar spectrum include surface sensitization, via decoration with plasmonic particles and/or narrow band gap semiconductors, as well as the introduction of dopants. 18,[21][22] Doping with earth-abundant metals, especially Cu, Fe and Sn, has been shown to enhance visible light absorption via band gap narrowing and reduced rates of surface recombination. [23][24][25][26][27][28][29][30][31] Furthermore, nanostructuring and morphological tuning further enhance physical properties through quantum confinement.…”

Inside‐and‐Out Semiconductor Engineering for CO2 Photoreduction: From Recent Advances to New Trends

“…Photocatalysts with 3D structure, such as nanosheets‐assembled flowers, [ 227–233 ] hollow spheres, [ 234–243 ] and hierarchical NW arrays, [ 244–252 ] have been widely developed. Due to their special features, including high specific surface area and high light utilization, they always demonstrate excellent photocatalytic CO 2 reduction performance.…”

On the effect of TiO2 nanocrystallites over the plasmonic photodegradation by Au nanoparticles

“…In principle, SPR‐mediated processes employing gold (Au) and silver (Ag) NPs enable the use of visible light as the energy input to drive a target transformation . Therefore, hybrid materials composed of plasmonic metal NPs and semiconducting materials, such as TiO 2 , represent attractive systems for the study of SPR‐mediated transformations and the effect of charge transfer over activities and selectivities . This is because semiconducting materials can act as electron acceptors, allowing for the transfer of hot electrons generated upon SPR excitation from metal NPs to the conduction band of the semiconductor.…”

“…Due to this enormous potential, many papers have focused on the investigation of the plasmonic and/or photocatalytic performances of TiO 2 –Au NPs hybrids . However, the usually described TiO 2 –Au NPs hybrids are often characterized by a not so precisely control over NPs size, monodispersed size distribution, and uniform distribution of Au and TiO 2 components.…”