Synergistic Effect Of Photocatalysis Research Articles

Fabrication of Ag–Cu2O/PANI nanocomposites for visible-light photocatalysis triggering super antibacterial activity

The Ag–Cu2O/PANI (ACP) was synthesized in a facile process. ACP significantly enhances photocatalytic performance of Cu2O, exhibits a high long-term sterilization activity, has a synergistic effect of photocatalysis and bacteriostatic action.

Synergistic effect of photocatalysis and pyrocatalysis of pyroelectric ZnSnO3 nanoparticles for dye degradation

In this work, the synergistic effect of the pyro-/photo-bi-catalysis of the sol-gel-synthesized ZnSnO3 nanoparticles is observed to enhance the dye wastewater decomposition ratio. Under the excitation of both the ultraviolet light and 20 °C–65 °C thermal cycles, using ZnSnO3 as catalyst, the bi-catalytic dye decomposition ratio is up to 98.1%, which is much higher than the photocatalytic decomposition ratio of 76.8% or the pyrocatalytic decomposition ratio of 20.2%. In bi-catalysis, the electrical polarization may promote the separation of photogenerated electron-hole pairs, which is helpful to improve the decomposition ratio of RhB dye wastewater. With these advantages of high dye decomposition ratio, recyclable and high energy utilization efficiency, the pyro-/photo-bi-catalysis of ZnSnO3 nanoparticles is potential in treatment dye wastewater in future.

Synergistic removal of organic pollutant and metal ions in photocatalysis-membrane distillation system

The removal of pollutants including aqueous organics and metal ions in the wastewater has been widely concerned. The coupled photocatalysis-membrane separation system can simultaneously realize the photoreaction of pollutants and their separation from wastewater to achieve the complete purification of wastewater. Herein, a photocatalysis-membrane distillation reactor (PMR) was designed to simultaneously remove the aqueous organics and metal ions for the wastewater treatment. The simultaneous removal of the probe pollutants, 4-chlorophenol (4-CP) and Ag+ ion, was successfully achieved via the synergistic effect of photocatalysis and direct contact membrane distillation (MD). Following the systematic investigation, it had been found that the rapid photo-reduction of Ag+ ions into Ag nanoparticles on BiOBr films was promoted by the coupling effect of the photo-degradation of 4-CP and the concentration effect of the membrane separation process. Meanwhile, the photo-degradation process of 4-CP was improved via the surface plasma effect and the promotion effect to photo-induced electron transfer of Ag nanoparticles. Furthermore, the photo-induced holes converted to act as the main active species for the oxidation of 4-CP in the synergistic PMR system, unlike the process in bare BiOBr system with the main active species of ·O2− radical. This synergistic photocatalysis-membrane separation system provided a valuable sight into the simultaneous removal of aqueous organics and metal ions for the practical applications.

Simple synthesis of WO3-Au composite and their improved photothermal synergistic catalytic performance for cyclohexane oxidation

Partial oxidation of cyclohexane (CHA) to KA oil (cyclohexanone (-one) and cyclohexanol (-ol)) with dry air is one of the most important industrial process. Despite great efforts have made in developing new catalysts, industrial processes are still limited by low conversion and selectivity with harsh condition. Here we report a significantly improved cyclohexane conversion and KA oil selectivity under solar light irradiation by anew photothermal synergistic catalyst, which was prepared by loading Au nanoparticles (Au NPs) onto WO3 nanosheets (WO3 NSs) with simple ultrasonic method. A high conversion of 9.0% and a high selectivity of 99.0% are acquired by WO3 nanosheets-Au nanoparticles (WO3-Au) composite under dry air, which are much higher than the simple sum of photocatalysis and thermal catalysis. The significantly improved catalytic properties of cyclohexane oxidation by the WO3-Au composite are mainly attributed to the improved light absorption, the effective charge separation and the synergistic effect of photocatalysis and thermal catalysis. The photothermal synergy to improve catalytic activity may be widely used in green industrial catalytic processes.

Construction of novel Z-scheme Ag/ZnFe2O4/Ag/BiTa1-xVxO4 system with enhanced electron transfer capacity for visible light photocatalytic degradation of sulfanilamide.

A novel Z-scheme system, Ag/ZnFe2O4/Ag/BiTa1-xVxO4 with enhanced electron transfer capacity was constructed for degrading sulfanilamide (SAM) using solar light. The photocatalytic activity of Ag/ZnFe2O4/Ag/BiTa1-xVxO4 was investigated. The effects of the mass ratio (ZnFe2O4:BiTaO4), doped V dose, Ag wt.% content, and irradiation time on the catalytic performance were evaluated. The reasonable mechanism of Ag/ZnFe2O4/Ag/BiTa1-xVxO4 solar photocatalytic degradation was also presented. These results reveal Ag/ZnFe2O4/Ag/BiTa1-xVxO4 possesses enhanced photocatalytic performance. The loaded Ag as electron mediator increases the electron transfer rate. Particularly, the doped V and the Fe ions from ZnFe2O4 form a powerful electron driving force, which enhances the electron transfer capacity. Ag/ZnFe2O4/Ag/BiTa1-xVxO4 shows optimal photocatalytic performance at 2.0 wt.% Ag and 0.5% doped V dose (ZnFe2O4:BiTaO4 = 1.0:0.5). Also, Ag/ZnFe2O4/Ag/BiTa1-xVxO4 exhibits high stability and repeatability in photocatalytic degradation. Several active species (•OH, •O2-, and h+) are produced in the Z-scheme photodegradation of SAM. These results on the enhanced photocatalytic activity of Ag/ZnFe2O4/Ag/BiTa1-xVxO4 are ascribed to synergistic photocatalytic effects of ZnFe2O4 and BiTa1-xVxO4 mediated through Ag and driven by doped V and Fe ions. Therefore, the Z-scheme Ag/ZnFe2O4/Ag/BiTa1-xVxO4 photocatalytic technology proves to be promising for the solar photocatalytic treatment of antibiotics under solar light.

Comparing potentiostatic and galvanostatic anodization of titanium membranes for hybrid photocatalytic/microfiltration processes

Hybrid photocatalysis/membrane processes constitute promising alternatives for water and wastewater treatment because they combine the efficiencies of filtration membranes technology and the oxidative effect of the photocatalytic process, increasing the lifetime of the membranes. The main challenge of these systems is the incorporation of the titanium dioxide (TiO2) catalyst without altering the filtration properties of the membrane and the photocatalytic activity of the catalyst. One way to achieve this goal is generating the TiO2 layer by direct anodization of titanium supports under controlled conditions to form titanium dioxide nanotubes (TiO2-NTs). This work reports the development of novel photocatalytic titanium membranes based on the formation of TiO2-NT arrays by anodization under both potentiostatic and galvanostatic conditions, and the scaling-up of the most promising systems to operational membrane photoreactors. The results demonstrated that the galvanostatic method displays more controlled tuneability to obtain NTs formation than the potentiostatic method on porous surfaces. However, despite the formation of TiO2-NTs structures, the observed photocatalytic activity is lower than that exhibited by TiO2 nanoparticles deposited directly on the membrane, although in this case the transmembrane pressure is significantly higher, and therefore the operational pumping costs are greater. Synergistic effects of photocatalysis and microfiltration are clearly demonstrated in the application of the hybrid system to the removal of bacteria for water disinfection processes, showing a significant improvement in the inactivation of E. coli bacteria in water with respect to the bare membrane.

Removal of Cr(VI) from water by a biochar-coupled g-C3N4 nanosheets composite and performance of a recycled photocatalyst in single and combined pollution systems

A series of biochar-coupled graphitic carbon nitride nanosheets (BPCMSs/g-C3N4 NSs) composites was successfully fabricated through a simple two-step calcination strategy by using waste Camellia oleifera shells (WCOSs) and melamine as raw materials. Hexavalent chromium [Cr(VI)] or total chromium (T-Cr) in water could be completely removed or mostly recovered through adsorption combined with photocatalytic reduction by using the as-prepared BPCMSs/g-C3N4 NSs. The adsorbed Cr(VI) on BPCMSs/g-C3N4 NSs could be reduced by photogenerated electrons into trivalent chromium ions (Cr3+) and stably fixed on BPCMSs/g-C3N4 NSs after strengthening. Interestingly, we found that the photocatalytic activity of the recycled Cr3+/BPCMSs/g-C3N4 NSs was remarkably improved compared with that of the fresh BPCMSs/g-C3N4 NSs for the degradation of aqueous organic pollutants. We tested the photocatalytic performance of the recycled Cr3+/BPCMSs/g-C3N4 NSs in the combined pollution system containing Cr(VI) and 4-fluorophenol (4-FP) and observed that a synergistic photocatalytic effect occurred in the Cr(VI)/4-FP combined pollution system under acidic and neutral conditions.

Construction of novel Z-scheme Ag/FeTiO3/Ag/BiFeO3 photocatalyst with enhanced visible-light-driven photocatalytic performance for degradation of norfloxacin

A novel Z-scheme Ag/FeTiO3/Ag/BiFeO3 with excellent visible-light-driven photocatalytic performance was constructed using sol-gel method followed by a photo-reduction process, and applied in the photocatalytic degradation of norfloxacin (NFX) in solution under visible light irradiation. The photocatalytic activities of Ag/FeTiO3/Ag/BiFeO3 and FeTiO3/BiFeO3 nanocomposites were compared. The effects of wt.% content of Ag, the mass ratio (FeTiO3:BiFeO3), and light irradiation time on the photocatalytic activities were assessed. The mechanism on Z-scheme Ag/FeTiO3/Ag/BiFeO3 photocatalytic degradation was also proposed. The results show that Ag/FeTiO3/Ag/BiFeO3 has higher photocatalytic activity than FeTiO3/BiFeO3, and the loading of Ag improves the photocatalytic activity of catalysts. The photocatalytic degradation extent reaches 96.5% within 150 min, when using Ag/FeTiO3/Ag/BiFeO3 at 2.0 wt% Ag (FeTiO3:BiFeO3 = 1.0:0.5). In addition, Ag/FeTiO3/Ag/BiFeO3 can be reused with excellent photocatalytic stability. The study reveals that the active species such as hydroxyl radicals (OH), holes (h+) and superoxide radicals (O2−) are generated during the photocatalytic process using Ag/FeTiO3/Ag/BiFeO3. These results on the enhanced photocatalytic activity are attributed to the synergistic photocatalytic effects of FeTiO3 and BiFeO3 with narrow band gaps mediated by Ag. Hence, the Z-scheme Ag/FeTiO3/Ag/BiFeO3 photocatalytic system demonstrates great promise in treating antibiotics in water and wastewater using solar energy.

A novel photoactive and three-dimensional stainless steel anode dramatically enhances the current density of bioelectrochemical systems

This study reports a high-performance 3D stainless-steel photoanode (3D SS photoanode) for bioelectrochemical systems (BESs). The 3D SS photoanode consists of 3D carbon-coated SS felt bioactive side and a flat α-Fe2O3-coated SS plate photoactive side. Without light illumination, the electrode reached a current density of 26.2 ± 1.9 A m−2, which was already one of the highest current densities reported thus far. Under illumination, the current density of the electrode was further increased to 46.5 ± 2.9 A m−2. The mechanism of the photo-enhanced current production can be attributed to the reduced charge-transfer resistance between electrode surface and the biofilm with illumination. It was also found that long-term light illumination can enhance the biofilm formation on the 3D SS photoanode. These findings demonstrate that using the synergistic effect of photocatalysis and microbial electrocatalysis is an efficient way to boost the current production of the existing high-performance 3D anodes for BESs.

Synergistic photocatalytic effect of porous g-C3N4 in a Cr(VI)/4-chlorophenol composite pollution system

The photocatalytic reduction of aqueous Cr(VI) to Cr(III) was preliminarily studied using porous g-C3N4 as a photocatalyst under acidic conditions. The observed synergistic photocatalytic effect of porous g-C3N4 on a Cr(VI)/4-chlorophenol (4-CP) composite pollution system was further studied under different pH conditions. Compared with single-component photocatalytic systems for Cr(VI) reduction or 4-CP degradation, the Cr(VI) reduction efficiency and 4-CP degradation efficiency were simultaneously improved in the Cr(VI)/4-CP composite pollution system. The synergistic photocatalytic effect in the Cr(VI)/4-CP composite pollution system can be attributed to the accelerated redox reaction between dichromate and 4-CP by electron transfer with porous g-C3N4.

One-step fabrication of g-C3N4 nanosheets/TiO2 hollow microspheres heterojunctions with atomic level hybridization and their application in the multi-component synergistic photocatalytic systems

In this paper, graphitic carbon nitride nanosheets/titanium dioxide hollow microspheres heterojunctions (g-C3N4 NSs/TiO2 HMSs) with excellent photocatalytic activity were successfully fabricated by a simple one-step synthesis strategy in the assistance of hydrothermal carbon microspheres. Hydrothermal carbon microspheres act as both dispersant and structure-directing agent for the simultaneous construction of graphitic carbon nitride nanosheets and titanium dioxide hollow microspheres. The synergistic photocatalytic effects in the 4-fluorophenol/hexavalent chromium [4-FP/Cr(VI)] and hexavalent chromium/trivalent arsenic [Cr(VI)/As(III)] multi-component composite pollution systems were studied by using as-prepared g-C3N4 NSs/TiO2 HMSs under different pH conditions. Interestingly, the efficiencies of 4-FP degradation, Cr(VI) reduction, and As(III) oxidation were simultaneously improved in the 4-FP/Cr(VI) and Cr(VI)/As(III) multi-component synergistic photocatalytic systems relative to the single-component photocatalytic systems. The synergistic photocatalytic mechanisms in the 4-FP/Cr(VI) and Cr(VI)/As(III) multi-component synergistic photocatalytic systems were systematically discussed.

Preparation and Photocatalytic Activity of TiO2-Wrapped Cotton Nanofiber Composite Catalysts

A novel TiO2-wrapped nanofiber composite catalyst, which possessed a unique porous structure and mixed crystalline phase, was prepared by the combination of superficial sol–gel and post-calcination processes. By means of the superficial sol–gel process, TiO2 layers were deposited on the surface of each nanofiber-like cellulose fiber, and then the TiO2-wrapped nanofiber composite catalysts were calcined at different temperatures under a nitrogen atmosphere. With temperature increasing, the original cotton nanofiber composites were converted into porous carbon nanofiber catalysts wrapped by a TiO2 mixed crystalline phase, which was accompanied by a crystal transformation. The photocatalytic activity of the new catalysts was evaluated by the degradation of methylene blue (MB) under ultraviolet (UV) irradiation. The results demonstrated that the new catalysts had good photocatalytic ability, and the TNC-700 catalyst showed a superior photocatalytic ability compared with the other catalysts; the new catalysts had a unique porous structure, high specific surface area, and mixed crystalline phase. Additionally, the synergistic photocatalytic effect of the TiO2 and activated carbon nanofiber resulted in the efficient degradation of organic pollutants in water or air.

Synergistic effect of photocatalysis and thermocatalysis for selective oxidation of aromatic alcohols to aromatic aldehydes using Zn3In2S6@ZnO composite

Selective oxidation of aromatic alcohols to corresponding carbonyl compounds under mild conditions has a promising prospect in industry. In the paper, we successfully prepared a new mode of photothermocatalyst, Zn3In2S6@ZnO composite, which shows dramatically enhanced activity for selective oxidation of benzyl alcohol to benzaldehyde compared with single Zn3In2S6 and ZnO under visible light illumination. The enhancement is due to a synergistic effect of low-temperature thermocatalysis on ZnO and photocatalysis on Zn3In2S6. ZnO could weaken bonds of the CHα and the OH. Then the reactive species (O2− and h+) generated on Zn3In2S6 could be easy for selective oxidation of benzyl alcohol to produce benzaldehyde. The photoelectrochemical and photoluminescence (PL) results and a series of control experiments (e.g. reaction temperature and radical scavenger) prove this synergistic effect and proposed mechanism. Moreover, the stable performance and high activity of Zn3In2S6@ZnO for other aromatic alcohols indicate its applicable potential. This study provides a promising way to combine photocatalysis and thermocatalysis for the design of novel and efficient visible-light-driven catalyst for selective oxidation of aromatic alcohols or other organics under mild reaction conditions.

A p-n heterojunction of CuI/TiO2 with enhanced photoelectrocatalytic activity for methanol electro-oxidation

In this paper, a p-n heterojunction including p-type CuI and n-type TiO2 is first time constructed to be the support for the deposition of Pt. The as-prepared Pt-CuI/TiO2 modified electrode is studied for the electrocatalytic oxidation of methanol both in dark and under light illumination. Compare to traditional electrocatalytic oxidation, the electrocatalytic activity of Pt-CuI/TiO2 for methanol oxidation is improved with 4.0 times upon light illumination. Moreover, compare to bare CuI and TiO2 upon light illumination, the heterostructure of CuI/TiO2 displays 4.3 and 9.1 times enhanced electrocatalytic activity for methanol oxidation, respectively. The synergistic effects of photocatalysis and electrocatalysis as well as the effective charge transport in the p-n heterojunction of Pt-CuI/TiO2 contribute such big enhancement. The present studies indicate that the constructing of p-n heterojunction provides more insights in the fields of photoelectrochemical and photo–assisted fuel cell system.

Preparation of the MoS2/TiO2/HMFs ternary composite hollow microfibres with enhanced photocatalytic performance under visible light

A novel route for synthesis of MoS2/TiO2/hollow microfibers (HMFs) ternary composite photocatalyst using sol-gel method combined with high temperature calcination under a nitrogen circumstances was reported for the first time. The morphology, structure and optical properties of the novel MoS2/TiO2/HMFs photocatalysts were fully characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), specific surface area (BET) and thermogravimetric analysis (TG). The photocatalytic activities were evaluated by photodegradating Methylene blue (MB) and Rhodamine B (RB) under visible light irradiation. The results showed the MoS2/TiO2/HMFs ternary composite hollow microfibre photocatalysts had a purification of more than 98.7% for MB and RB of simulating wastewater, and acquired the superior synergistic effect of adsorption and catalysis for organic pollutants. That’s because the sensitization of MoS2 enlarged the wavelength response range to the visible region of the solar spectrum, the HMFs could beneficially increase adsorption capability for organic pollutants, and the mixed crystalline phase of TiO2 accelerated the decomposition of organic pollutant. A detailed study of involved active species unraveled the mechanism regarding photocatalysis. So, the synergistic photocatalytic effect of HMFs, TiO2 and MoS2 was very important and significant for wastewater treatment or prevention of air pollution.

Characterization of Sputtered HfO2−x –TiO2−x Nanocolumn Arrays and Their Application in Photocatalysis

The physical and chemical properties of sputtered HfO2−x–TiO2−x nanocolumn arrays and the photocatalytic action of high-\(\varepsilon\) (HfO2) nanocolumns for decomposition of methylene blue have been studied. Fabrication of HfO2−x–TiO2−x nanocolumn array composites by reactive sputtering without further treatment was comprehensively investigated. Well-isolated HfO2−x nanocolumns with maximum separation of approximately 500 nm and excellent orientation normal to the substrate were obtained. The coupling between HfO2−x and TiO2−x was found to be crucial for enhanced photocatalytic action; the optimal coupling was identified for HfO2−x–TiO2−x nanocolumn composites with four pairs of alternating layers, which showed better performance (by approximately 25%) under 30 W of ultraviolet (UV) irradiation, compared with TiO2−x thin films. The synergistic photocatalytic effect was predominantly attributed to defect-induced electron migration along the HfO2−x nanocolumn structure. In addition, the corresponding photoluminescence spectra and energy band diagram for the HfO2−x–TiO2−x system were used to complement the photocatalytic results.

Synthesis, characterization and synergistic photocatalytic properties of yeast-assisted composite La0.7Sr0.3MnO3/TiO2

A magnetic yeast-assisted composite Y-La0.7Sr0.3MnO3/TiO2with p–n heterojunction was prepared. And it shows an obvious synergistic photocatalytic effect on methyl orange (MO) wastewater under solar irradiation.

Algae decorated TiO2/Ag hybrid nanofiber membrane with enhanced photocatalytic activity for Cr(VI) removal under visible light

Algae as an abundant natural biomass, more attention has been paid to explore its potential application in environmental pollutants treatment. This work prepared the algae-TiO2/Ag bionano hybrid material by loading algae cells on the ultrafine TiO2/Ag chitosan hybrid nanofiber mat. For the first time, the synergistic photocatalytic effect of fresh algae and TiO2/Ag nanomaterial was investigated by removal of Cr(VI). The addition of algae significantly improved the photo-removal of Cr(VI) in the system with TiO2/Ag hybrid nanomaterial under visible light irradiation. Meanwhile, the photocatalytic mechanism was studied. The photogenerated reactive oxygen species were quantified and the addition of algae apparently decreased the yields of OH to 31.0μM, while improved the yields of 1O2 and O2− in the reaction system with TiO2/Ag hybrid nanofiber mats. The change of superoxide dismutase activity and malondialdehyde content in algae indicated that TiO2/Ag could impose oxidative stress and cause lipid peroxidation in algae cells. During the course of irradiation, algae released substances could act as scavenger for holes, thus inhibited the recombination of hole/electron and enhanced the photocatalytic reduction of Cr(VI) by electrons on TiO2 surface. Algae was simultaneously photodegraded in the system and the resulting O2−, organic free radicals could promote the reduction of Cr(VI). This functional hybrid nanofiber mat was easily recovered and maintained a great photocatalytic activity on the five successive cycles. This algae-photocatalyst hybrid material has promising applications potential in heavy metal removal and organic pollutants treatment.

Visible-light-induced dendritic BiVO4/TiO2 composite photocatalysts for advanced oxidation process

Visible-light-induced dendritic BiVO4/TiO2 photocatalysts have been successfully synthesized via a composite hydrothermal and sol-gel method. Evaluated by the degradation of methylene blue (MB) under visible-light irradiation (420 nm < λ < 800 nm), the sample with ratio of BiVO4/TiO2 (mass ratio) equal to 60% prepared at 400 °C exhibited the best photocatalytic activity. The appropriate band gap (BiVO4 provided) availed the absorption of visible light and the larger surface area (TiO2 provided) enhanced the adsorption ability towards the pollutants, resulting in the high separation ratio of the electrons and holes generated. Through further detecting the degradation mechanism, it was proposed a new idea that the best activity mainly depended on the synergistic effect of photocatalysis and photosensitization. The active species generated in the degradation processes were mainly derived from BiVO4 and MB, while TiO2 was just the transporter of charge carriers. Some evidence has been provided to support this conclusion in detail. These results would be useful to develop highly efficient photocatalysts and helpful to reveal the degradation mechanism clearly.

ZnO nanoflowers photocatalysis of norfloxacin: Effect of triangular silver nanoplates and water matrix on degradation rates

Abstract Norfloxacin (NF) is an effective antimicrobial drug that poses a threat to human health because of its environmental residues. In this research, ZnO nanoflowers and triangular silver nanoplates (T-Ag) were synthesized using a facile sol–gel method. The synergistic photocatalytic effects of the adding different triangular silver nanoplates concentration over ZnO nanoflowers on the NF removal under visible light was studied for the first time. Photodegradation results demonstrated that T-Ag could significantly enhance the activity of ZnO nanoflowers. The degradation efficiency of NF by T-Ag/ZnO nanoflowers was affected in the different water matrices, including ultra-pure, tap, and river water. The effects of the dosage of ZnO nanoflowers, initial NF concentration, and pH on the photocatalytic activity of ZnO nanoflowers were also explored. The results show that the highest rate constant for the degradation of NF is obtained with 1 mg L −1 of T-Ag, 0.1 g L −1 of ZnO, initial NF concentration of 10 mg L −1 , and pH of 11 in ultra-pure water. The possible mechanism of the photocatalytic degradation of NF using T-Ag/ZnO nanoflowers through the addition of scavenger agents (i.e., EDTA and methanol) was also studied.