Fabrication Of Plasmonic Composite Photocatalysts And The Mechanism Of Degradation Of Organic Pollutants

The production and widespread use of organic dyes inevitably causes water pollution, thereby poses potential threat to human and ecological health. With the increasingly serious water pollution, it is imperative that some effective measures need be taken to remove dyes from dyeing wastewater. The traditional techniques of dye removal from wastewater in the degradation efficiency and harmless processing are still far from satisfactory. Therefore, the development of efficient and environment-friendly technique to treat dye wastewater is becoming a hot topic. The photocatalytic degradation of dye is green and efficient wastewater treatment technology, but the traditional photocatalyst (such as TiO2) has narrower spectral response, and the easy recombination of photoinduced charges, which seriously restricts the practical applications. In order to improve the optical absorption and carrier separation efficiency of the photocatalyst, this paper proposes a strategy for fabricating new photocatalyst, which combined with the surface plasmon resonance effect of noble metal and the characteristics of composite photocatalytic material, so as to improve the photocatalytic activity for degradation of aqueous dyes under visible-light.One dimensional β-AgVO3 nanoribbon was synthesized via in-situ hydrothermal approach;the modification of Ag nanoparticles on surfaces was obtained by reduction of Ag+ on AgVO3 surfaces by NaBH4. The in-situ growth of Ag on AgVO3 nanoribbon is an important approach to achieve the robust bonding between Ag andAgVO3 nanoribbon, which is essential for the effective charge transfer and separation during photocatalysis. Ag nanoparticles formed on photocatalyst surfaces were synthesized usually by photoreduction which is a complicated and time-consuming method due to the additional photoreduction devices such as xenon lamp and longer reaction time. Herein, the present synthesis method is facile and time saving. This simple synthetic route, which involves no additional photoreduction device, will offer great opportunities for the scale-up in suit preparation of other Ag-loaded Ag-based composite materials. For 20 mg/L BF solution, about 93.6% of BF was decomposed over 0.05-Ag/AgVO3 (1 g/L) with 90 min of visible-light irradiation. The finite difference time domain (FDTD) simulation analysis indicates the formed Ag nanoparticles induce the localized surface plasmon resonance (SPR) leading to increased electric field and the enhanced absorption of visible light. In addition, the presence of Ag nanoparticles could narrow the band gap energy from 2.01 eV for AgVO3to 1.50 eV for Ag/AgVO3. The hybridization of O 2p and Ag 4d orbits of AgVO3 is weak, which facilitates transfer of valence band electrons into the conduction band.Ag/AgVO3/C3N4 ternary plasmonic photocatalysts were synthesized by a facile one-step in-situ hydrothermal method. This is the first experimental example in which the self-assembling 1-D AgVO3 nanoribbons on the surface of 2-D C3N4 ultrathin nanosheets and Ag nanoparticles generated from AgNO3 decomposition were achieved simultaneously. The as-obtained Ag/AgVO3/C3N4 ternary plasmonic photocatalyst was investigated to catalytically degrade basic fuchsin (BF, a model organic pollutant) under visible light irradiation. For 20 mg/L BF solution, about 99.3% of BF was decomposed over Ag/AgVO3/C3N4 (1 g/L) with 70 min of visible-light irradiation. The explanation for the enhanced photocatalytic performance observed from the Ag/AgVO3/C3N4 ternary plasmonic photocatalyst is proposed. First, the SPR absorption of Ag nanoparticles will remarkably enhance the absorbance of the Ag/AgVO3/C3N4 in the visible light region. Therefore, the formation rate of electron-hole pairs on the sample increases substantially, resulting in better catalytic performance. Second, the hybridization of C3N4 species in Ag/AgVO3/C3N4 not only facilitates the adsorption of pollutant molecules, but also promotes the charge transfer between AgVO3 and C3N4. Additionally, the widths of Ag/AgVO3 nanoribbons in the case of Ag/AgVO3/C3N4 are smaller than that of bare Ag/AgVO3 nanoribbons, which may also contribute partially to the enhanced photocatalytic performance.We report for the first time the successful attempt at the fabrication of Ag/AgVO3/RGO ternary plasmonic photocatalyst through a facile one-step in-situ hydrothermal method, in which the crystallization of AgVO3, Ag nanoparticles generated from AgNO3 decomposition and reduction of GO to RGO were achieved simultaneously. In this innovative hybrid structure,1-D Ag/AgVO3 nanoribbons should be uniformly dispersed on 2-D RGO nanosheet surfaces. The as-obtained Ag/AgVO3/RGO ternary plasmonic photocatalyst would exhibit excellent light-trapping ability and catalytic performance. For 20 mg/L BF solution, about 96.1% of BF was decomposed over Ag/AgVO3/RGO (1 g/L) with 70 min of visible-light irradiation. We propose an explanation for the enhanced photocatalytic performance observed from the Ag/AgVO3/RGO ternary plasmonic photocatalyst. Firstly, Ag nanoparticles play the important role on the property of the photocatalyst. The strong SPR absorption of Ag nanoparticles will remarkably enhance the absorbance of the samples in the visible light region. Therefore, the formation rate of electron-hole pairs on the sample increases substantially, resulting in better catalytic performance. In addition, the hybridization of RGO species in Ag/AgVO3/RGO not only facilitates the adsorption of pollutant molecules due to the non-covalent intermolecular π-π interactions between the pollutant molecules and RGO nanosheets, but also promotes the fast and long-range interfacial charge transfer along the π-π graphitic carbon network owing to RGO with high conductivity. Lastly, the widths of Ag/AgVO3 nanoribbons in the case of Ag/AgVO3/RGO are smaller than that of bare Ag/AgVO3 nanoribbons, which may also contribute partially to the enhanced photocatalytic performance. Moreover, as suggested by our XPS spectra, the 1-D Ag/AgVO3 nanoribbons and 2-D RGO nanosheets may serve as electron donor and electron acceptor, respectively, in the Ag/AgVO3/RGO ternary plasmonic photocatalyst. Thus, the electrons originally photogenerated on the 1D Ag/AgVO3 nanoribbons can migrate into 2-D RGO nanosheets through a percolation process during the photocatalytic reaction.