A Study On Synthesis And Photocatalytic Performance Of WO3-Nanoplates-Based Hierarchical Nanocomposites

Hierarchical semiconductor nanocomposites have potential applications in photocatalytic degradation of organic dyes, owing to its high surface areas and abundant active sites. In addition, the hierarchical semiconductor cnanoomposites can separate photoinduced electrons and holes effectively because of the coupling of various semiconductors with different energy bands. In this paper, a series of hierarchical Wo3-nanoplates-based nanocomposite were perpared by coupling WO3nanoplates with TiO2, CdS and Ag/AgCl nanoparticles, respectively, and their photocatalytic properties under visible-light irradiation were investigated.Single-crystalline WO3nanoplates were systhesied using commercial tungstic acid (H2WO4) powder as the starting material via a tungstate-based inorganic-organic intermediate hybrid. The two-dimensional WO3nanoplates with dimenssions of (100-～250)×(250～350)×(10-30) nm can overcome the agglomeration problem due to the steric effect of "House of Cards", and have high surface areas. The WO3nanoplates obtained are, therefore, the unique candidate for the substrates to construct hierarchical semiconductor nanocomposite photocatalysts.WO3-doped TiO2fibers were prepared by electrosinning using tetrabutyl titanate as a Ti source. The diameters of the as-prepared TiO2fibers are about1～2μm and the WO3nanoplates are uniformly dispersed in the TiO2fibers. With an increase in the amount of WO3nanosheets, the rutile TiO2fibers are transformed to anatase TiO2fibers that became easy to break. In addition, the RhB absorption of the TiO2fibers with more WO3nanoplates becomes stronger and stronger.The CdS/WO3-nanoplate nanocomposites were prepared via a wet chemical method. The hexagonal CdS nanoparticles with a size of about20nm uniformly anchored on the surfaces of the WO3nanoplates. When the molar ratio of CdS to WO3is1:5, the as-prepared CdS/WO3nanocomposite has an optimal photocatalytic property, i.e., finishing degradation of the10mg/L RhB in336min under visible-light irradiation. The photocatalytic efficiency is greatly improved because the CdS/WO3composite can absorb more visible light and can effectively separate photoinduced electrons and holes. The TiO2/WO3-nanoplate composite was prepared using a hydrothemal method. The rutile TiO2phase with a size of about10nm uniformly dispersed on the surfaces of the WO3nanoplates. The TiO2/WO3nanocomposite with a moar W/(W+Ti) ratio of21.2%obtained at150℃for24h has an optimal photocatalytic property, completely disgrading a10mg/L RhB aq. solution in80min. The results indicate that the photocatalytic efficiency is greatly improved because the TiO2/WO3composite can partly absorb visible light and separate photoinduced electrons and holes effectively.The hierarchical photocatalysts of Ag/AgCl@WO3nanoplates were synthesized by anchoring Ag/AgCl nanocrystals on the surfaces of WO3nanoplates. The heterogeneous precipitation process of the PVP-Ag+-WO3suspensions with a Cl-solution added drowise was developed to synthesize AgCl@WO3composites, which were then photoreduced to in situ form Ag/AgCl@WO3nanostructures. The hierarchical photocatalysts of Ag/AgCl@WO3nanoplates will absorb visible light and separate the photoinduced electrons and holes, owing to the combination between the surface plasmon resonance (SPR) effect and band synergy effect. Thereby, the hierarchical photocatalysts of Ag/AgCl@WO3nanoplates have enhanced photocatalytic activity under visible light irradiation.