Hierarchically plasmonic photocatalysts of Ag/AgCl nanocrystals coupled with single-crystalline WO3 nanoplates

Abstract

The hierarchical photocatalysts of Ag/AgCl@plate-WO₃ have been synthesized by anchoring Ag/AgCl nanocrystals on the surfaces of single-crystalline WO₃ nanoplates that were obtained via an intercalation and topochemical approach. The heterogeneous precipitation process of the PVP-Ag⁺-WO₃ suspensions with a Cl⁻ solution added drop-wise was developed to synthesize AgCl@WO₃ composites, which were then photoreduced to form Ag/AgCl@WO₃ nanostructures in situ. WO₃ nanocrystals with various shapes (i.e., nanoplates, nanorods, and nanoparticles) were used as the substrates to synthesize Ag/AgCl@WO₃ photocatalysts, and the effects of the WO₃ contents and photoreduction times on their visible-light-driven photocatalytic performance were investigated. The techniques of TEM, SEM, XPS, EDS, XRD, N₂ adsorption-desorption and UV-vis DR spectra were used to characterize the compositions, phases and microstructures of the samples. The RhB aqueous solutions were used as the model system to estimate the photocatalytic performance of the as-obtained Ag/AgCl@WO₃ nanostructures under visible light (λ ≥ 420 nm) and sunlight. The results indicated that the hierarchical Ag/AgCl@plate-WO₃ photocatalyst has a higher photodegradation rate than Ag/AgCl, AgCl, AgCl@WO₃ and TiO₂ (P25). The contents and morphologies of the WO₃ substrates in the Ag/AgCl@plate-WO₃ photocatalysts have important effects on their photocatalytic performance. The related mechanisms for the enhancement in visible-light-driven photodegradation of RhB molecules were analyzed.

Hierarchically Z-scheme photocatalyst of Ag@AgCl decorated on BiVO4 (0 4 0) with enhancing photoelectrochemical and photocatalytic performance

“…It can be clearly seen that almost all of the samples exhibit strong absorption in the visible light region except AgCl. Here, the photocatalyst of Ag/BiVO 4 exhibits a better light absorption than the others due to the more amount of loading metallic Ag 0 species on the crystal facet of BiVO 4 (0 4 0), which can be attributed to the surface plasmonic resonance (SPR) effect of Ag 0 NPs [34]. The absorbance of obtained Ag@AgCl/BiVO 4 heterostructure is between the pristine BiVO 4 and Ag/BiVO 4 , which could be interpreted that some AgCl formed on the surface of Ag NPs and thus hindered the SPR-effect of Ag 0 .…”

Tungsten-based nanomaterials (WO 3 & Bi 2 WO 6 ): Modifications related to charge carrier transfer mechanisms and photocatalytic applications

“…The TiO 2 present as over layer on WO 3 can also improve the chemical stability of WO 3 . Rather than this trivial approach, the deposition of metal on this composite surface that results in equal The integration of Ag-AgCl on WO 3 with varied morphologies like NPs, hollow sphere with flower-like, nanorods and nanoplates was active for the degradation of various organic pollutants under visible light [124][125][126]. The distribution of Ag and AgCl is largely heterogeneous and this composite absorbs over the entire wavelength range of solar spectrum.…”

“…The high activity of this plasmonic photocatalyst are attributed to: (i) assemblage and conjugation of Ag-AgCl on WO 3 surface introduces large number of interfaces between Ag-AgCl and WO 3 to provide more active sites for the degradation reactions; (ii) electrons in WO 3 CB can be transferred to Ag to initiate dioxygen reduction, while holes in the VB oxidize the dye molecules (Fig. 4); (iii) electronic coupling of Ag-AgCl and WO 3 nanocrystals improved the charge separation [124][125][126]. In all these cases, the ratio of Ag 0 /Ag + played a crucial role in tuning the visible light response and photocatalytic activity.…”

Regulations of silver halide nanostructure and composites on photocatalysis

“…Heterogeneous system constituted by photoactive semiconductors is regarded as an effective method to facilitate the photoexcited electron-hole separation with enhanced photocatalytic activity [254][255][256][257][258][259][260][261][262][263][264][265][266][267][268][269]. Various metallic semiconductor (such as TiO 2 , ZnO, BiVO 4 ) and metal-free nitrogen-doped graphene semiconductors have been considered as preferred substances to composite with AgX, shown as Table 2.…”