Plasmon Mediated Photocatalysis by Solar Active Ag/Zno Nanostructures: Degradation of Organic Pollutants in Aqueous Conditions (original) (raw)
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We report the synthesis of Ag-ZnO hybrid plasmonic nanostructures with enhanced photocatalytic activity by a facile wet-chemical method. The structural, optical, plasmonic and photocatalytic properties of the Ag-ZnO hybrid nanostructures were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL) and UV-visible absorption spectroscopy. The effects of citrate concentration and Ag nanoparticle loading on the photocatalytic activity of Ag-ZnO hybrid nanostructures towards sun-light driven degradation of methylene blue (MB) have been investigated. Increase in citrate concentration has been found to result in the formation of nanodisk-like structures, due to citrateassisted oriented attachment of ZnO nanoparticles. The decoration of ZnO nanostructures with Ag nanoparticles resulted in a significant enhancement of the photocatalytic degradation efficiency, which has been found to increase with the extent of Ag nanoparticle loading.
Synthesis and characterization of plasmonic visible active Ag/ZnO photocatalyst
Ag deposited ZnO nanoparticles (NPs) have been synthesized by simple sol-gel method for visible light active photocatalytic application. X-ray diffraction (XRD), TEM, UV-DRS and PL studies have been used to characterize the photocatalyst. The results show that Ag/ ZnO NPs are wurtzite phase (WZ) of ZnO with Ag NPs in the surface region forming a hetero-interface of Ag-WZ (ZnO). Visible light activity of the material has been studied using photocatalytic degradation kinetics of methylene blue as a probe pollutant. Ag/ZnO NPs exhibit five times higher visible-light driven photocatalytic activity than pristine ZnO and four times than the reference Degussa P-25, under identical conditions. The high visible activity of Ag/ZnO may be attributed to the surface plasmon effect complemented sensitization in the presence of metallic Ag and effective charge separation through Ag-WZ hetero-interfaces.
Applied Surface Science, 2019
Plasmonic metal-semiconductor nanostructures endow them with an enormous potential application in photocatalysis, however, the uniform deposition of metal NPs as small as a few nanometers remains a challenge. Here, we demonstrate the effectiveness of two-step polymer-network gel process in the synthesis of Ag-ZnO nanocatalyst with superior photocatalytic properties. Because of uniform distributed Ag NPs, large specific surface area and abundant surface oxygen vacancies, the Ag-ZnO nanoparticles exhibit a super high photocatalytic efficiency in comparison to pure ZnO nanoparticles. The efficiency can be further improved by optimizing the external factors, such as catalyst dosage, ambient temperature and initial solution pH. Good stability and practicability indicate its potential application in environmental purification. Our work does not only provide a feasible strategy for the synthesis of high property Ag-ZnO nanophotocatalysts, but also enriches the understanding of metal-metal oxide nanostructures.
Chinese Journal of Catalysis, 2014
AgX (X = I, Br) nanoparticles-surface modified ZnO nanorod arrays (AgX/ZnO) were prepared using an impregnation method. The influence of impregnating solution concentration, immersion time, and UV light illumination pretreatment on the visible light-driven photocatalytic activity of AgX/ZnO was evaluated. The morphology, phase composition, band gap, and surface characteristics of the AgX/ZnO nanorod arrays were assessed by field-emission scanning electron microscopy, X-ray diffraction, diffuse reflectance UV-Vis absorption spectroscopy, and X-ray photoelectron spectroscopy. The AgBr nanoparticles were homogeneously distributed on the top and side surfaces of the ZnO nanorods, and connected to form a porous network structure. Following UV light illumination pretreatment, Ag nanoparticles were formed on the surface of the AgBr nanoparticles producing a Ag/AgBr/ZnO nanostructure. Methyl orange photodegradation study showed that the photocatalytic activity of AgBr/ZnO was higher than that of AgI/ZnO, synthesized under similar conditions, and was highly related to the impregnating solution concentration and immersion time. Owing to the high surface area of the ZnO nanorod arrays, the visible light sensitivity of AgBr, and surface plasmon resonance of Ag/AgBr, Ag/AgBr/ZnO exhibited the highest visible light-driven photocatalytic activity.
Advanced Powder Technology
Ag/Ag 2 S-ZnO nanocomposites were prepared via a simple hydrothermal process followed by a plasmonic Ag + reduction through a photo-deposition method. Ag 2 S was introduced to narrow the overall composite bandgap and activate the surface plasmon resonance (SPR) effect of the Ag + cation present. The physicochemical properties of the as-synthesised catalysts were characterised by X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM and TEM), Brunauer-Emmett-Teller (BET) analysis. Fourier-transform infrared spectroscopy (FTIR), Ultraviolet diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence emission spectra (PL) and X-ray photoelectron spectroscopy (XPS) was conducted to investigate the photo-absorption and emission spectra of the nanocomposites. The degradation efficiency of all the synthesised catalysts (ZnO, Ag 2 S, Ag/ZnO and Ag 2 S/ZnO) prior to the final product, Ag/ Ag 2 S/ZnO was tested and compared. Results showed that the ternary Ag/Ag2S/ZnO achieved a 98 % phenol removal compared to 50 %, 11 %, 64 % and 93 % for ZnO, Ag2S, Ag/ZnO and binary Ag2S/ZnO, respectively. The degradation kinetics followed the Langmuir-Hinshelwood model, which typically describes heterogeneous photocatalytic surface reactions. The linear fits had R 2 values higher than 0.97, which confirms the degree of accuracy or statistical fitness to the kinetic model. Degradation scavenger test confirmed the holes (h +) as the main inhibitor and identified the superoxide O 2 radical as the main active specie responsible for the degradation. Total organic carbon analysis using the ternary Ag/Ag 2 S-ZnO catalyst only achieved a 74% phenol mineralization after 24 h of photocatalysis. Recyclability tests showed good phenol removal stability of Ag/Ag 2 S-ZnO at 41 % after five recycle runs. Hence, a synergistic degradation mechanism responsible for the efficient photo-degradation performance was proposed.
Enhanced photocatalytic activity of Ag nanostructures
2018
Noble metal/semiconductor oxide nanocomposites have considerable interest on degradation of pollutants from textile wastewaters. Ag-ZnO, as one of the noble metal/semiconductor oxide nanocomposite, is highly efficient catalyst in textile pollutant degradation that allows irradiation wavelength towards visible light region. Application of Ag on the surface of ZnO nanoparticles has caused e its greater degradation efficiency. Oxidation of the methylene blue consumes photo efficiently, blocking the electron-hole recombination and thus, increasi scavenger of the photogenerated electrons.
Ag/ZnO nanoparticles thin films as visible light photocatalysts
RSC Adv., 2014
Silver (Ag) and zinc oxide (ZnO) nanoparticles were simultaneously deposited on a glass substrate using the radio frequency (RF) sputtering technique at different substrate temperatures. Detailed characterization of the co-sputtered Ag/ZnO thin films was performed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS). The as synthesized thin films were tested using UV-Vis diffuse reflectance spectroscopy to evaluate their optical properties. The obtained SEM results show a uniform dispersion of Ag nanoparticles within the ZnO matrix. These nanoparticles have average particle size of 20 nm. The optical band gap value was calculated from UV transmission spectra of Ag/ZnO thin films deposited at various substrate temperatures. This value was observed to be in the visible light range (i.e., 2.7-3.1 eV), which is much smaller than that of pure ZnO (3.37 eV). The photocatalytic activity of the produced thin films was evaluated through visible light photodegradation of 2-chlorophenol (2-CP) which has been used as a pollutant model in water. The synthesized thin films showed enhanced visible light photocatalytic efficiency towards 2-CP degradation at elevated substrate temperature and retained their catalytic efficiency with only 8% loss in efficiency after four reuse cycles. Kinetic parameters involved in the degradation process were investigated by applying a pseudo-second-order kinetic model.
Ag/Ag2S-ZnO nanocomposites were prepared via a simple hydrothermal process followed by a plasmonic Ag+ reduction through a photo-deposition method. Ag2S was introduced to narrow the overall composite bandgap and activate the surface plasmon resonance (SPR) effect of the Ag+ cation present. The physicochemical properties of the as-synthesised catalysts were characterised by X-ray diffraction (XRD) to determine the crystallinity, while scanning and transmission electron microscopies (SEM and TEM) revealed the particle size and morphology. The surface area and pore sizes were measured using a Brunauer-Emmett-Teller (BET) analysis. Fouriertransform infrared spectroscopy (FTIR), Ultraviolet diffuse reflectance spectroscopy (UV-vis DRS) and photoluminescence emission spectra (PL) was conducted to investigate the photo-absorption and emission spectra of the nanocomposites. X-ray photoelectron spectroscopy (XPS), confirmed the surface electrochemical states and electron transfer between Ag/Ag2S and ZnO. Ternary Ag/Ag2S-ZnO catalyst demonstrated an excellent photo-generated charge separation efficiency by achieving 98% phenol degradation higher than ZnO, Ag/ZnO and Ag2S-ZnO composites due to its enhanced photosensitivity and SPR effect combined. The degradation for all the synthesized catalysts followed the Langmuir-Hinshelwood model, which typically describes heterogeneous photocatalytic surface reactions. All the fits had R2 values higher than 0.97, which confirms the degree of accuracy or statistical fitness to the kinetic model. Total organic carbon analysis using the ternary Ag/Ag2S-ZnO catalyst only achieved a 74% phenol mineralization after 24 hours of photocatalysis. Recyclability tests showed good degradation stability of Ag/Ag2S-ZnO after five recycle runs. Hence, a synergistic degradation mechanism responsible for the efficient photodegradation performance was proposed.
International Journal of Photoenergy, 2020
Zinc oxide (ZnO) has been known as an excellent photocatalyst for the degradation of a variety of organic pollutants under UV irradiation. This work describes a synthesis of ZnO nanoparticles via a facile precipitation method, and Ag was doped into Ag/ZnO nanocomposite to improve the photocatalytic degradation of BPA under visible light irradiation. The obtained ZnO nanoparticles were 20 nm in size and had a relatively high surface area and pore volume, 26.2 m2/g and 0.48 cm3/g, respectively. The deposition of Ag led to a decrease in the surface area, pore volume, and band gap energy ( E g ) of ZnO nanoparticles. However, the photocatalytic activity of Ag/ZnO composite in the case increased. The performance of ZnO was compared with Ag/ZnO composites at the different molar ratios, and the kinetic reaction of BPA in these catalysts was investigated by the first-order kinetic model. The sample of Ag/ZnO-10 composite had the highest catalytic activity and showed the degradation efficien...