Synthesis,characterization, and visible-light photocatalytic activity of transition metals doped ZTO nanoparticles

Transition metals doping has been proved to be a feasible way for tuning the physical properties on the surface and bulk of nanomaterials and also for the good performance in decontamination of emerging pollutants. In this context, doped samples of zinc tin oxide or zinc stannate nanoparticles (ZTO NPs) by several transition metals were synthesized in order to enhance the optical absorbance with the aims of reducing the band gap and therefore ameliorated their photocatalytic activity. They were characterized by the X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy, Raman spectroscopy and photoluminescence. The XRD patterns and the microscopic observations showed the formation of spherical nanoparticles with an average size of about 30 nm and highly pure ZTO phase with an inverse spinel structure. The Raman spectra were dominated by bands relatives to the F2g (2) and A1g symmetries modes of inverse spinel structure. The band gap Eg is estimated to be 3.75 eV for the undoped sample, and 3.67, 3.64, 3.78 and 3.21 eV, for 2% Fe, 2% Mg, 2% Gd, and 2% Mn doped ZTO samples, respectively.Furthermore, the undoped ZTO NPs have the intrinsic problem of recombination of photogenerated charge carriers. We have shown that the reduction of the band gap and oxygen vacancies resulting from the doping effect could be a useful tool for trapping and avoid the recombination of electrons coming from photosensitized rhodamine B (RhB) under visible light irradiation. Owing to the structural advantages and low band gap, 2% Mn doped ZTO NPs, with the kinetic rate constants k of 0.024 min⁻¹, show enhanced performance for the elimination of RhB in aqueous solution compared to undoped and other doped ZTO NPs.     

Fabrication of bacterial cellulose with high efficient loading of Ag and TiO2 nanoparticles for removing organic dyes

As a new advanced oxidation technology, photocatalytic technology has broad application prospects in the field of wastewater treatment. However, in the actual use process, there will be difficulties in catalyst recovery and reuse. This article successfully prepared bacterial cellulose (BC) loaded silver and titanium dioxide nanoparticles (Ag-plated TiO₂/BC composite pellicle) by in situ embedding method. BC not only works as the carrier to load TiO₂ and Ag NPs but also adsorbs dyes to promote the reaction. As a reusable photocatalytic film, it is convenient to use and recycle in terms of testing and characterization compared with powders. The results show that Ag and TiO₂ nanoparticles were closely embedded in BC. We evaluated the photocatalytic degradation performance of the catalyst on methylene blue (MB), active red X-3B, and Rhodamine B. When the reaction time was 2 h, the dye removal rates were 71%, 68%, and 82.6%. At the same time, through the inhibition zone experiment, it was found that the material has a certain inhibitory effect on both Escherichia coli and Staphylococcus aureus. Therefore, the supported catalyst prepared by this method has the advantages of high catalytic activity, relatively stable property, easy recovery, and tailorability, making it potentially applicable in sewage post-treatment links.     

Gas‐phase removal of indoor volatile organic compounds and airborne microorganisms over mono‐ and bimetal‐modified (Pt,Cu, Ag) titanium(IV) oxide nanocomposites

The photocatalytic deactivation of volatile organic compounds and mold fungi using TiO₂ modified with mono‐ and bimetallic (Pt, Cu, Ag) particles is reported in this study. The mono‐ and bimetal‐modified (Pt, Cu, Ag) titanium(IV) oxide photocatalysts were prepared by chemical reduction method and characterized using XRD, XPS, DR/UV‐Vis, BET, and TEM analysis. The effect of incident light, type and content of mono‐ and bimetallic nanoparticles deposited on titanium(IV) oxide was studied. Photocatalytic activity of as‐prepared nanocomposites was examined in the gas phase using LEDs array. High photocatalytic activity of Ag/Pt‐TiO₂ and Cu/Pt‐TiO₂ in the reaction of toluene degradation resulted from improved efficiency of interfacial charge transfer process, which was consistent with the fluorescence quenching effect revealed by photoluminescence (PL) emission spectra. The photocatalytic deactivation of Penicillium chrysogenum, a pathogenic fungi present in the indoor environment, especially in a damp or water‐damaged building using mono‐ and bimetal‐modified (Pt, Cu, Ag) titanium(IV) oxide was evaluated for the first time. TiO₂ modified with mono‐ and bimetallic NPs of Ag/Pt, Cu, and Ag deposited on TiO₂ exhibited improved fungicidal activity under LEDs illumination than pure TiO₂.     

Fabrication of TiO2 photocatalytic electrode and contamination control with atmospheric pressure O2 plasma jet

In this study, we demonstrate the fabrication of TiO₂ photocatalytic electrode by sol-gel and electrospinning technique. The anatase TiO₂ nanofiber is successfully formed after thermal annealing at 260°C. As-prepared TiO₂ photocatalytic electrode contains surface contamination, which includes a polymer binder such as ethyl cellulose, carbon by carbonization of polyvinylpyrrolidone, and residue polyvinylpyrrolidone. To efficiently remove the surface contaminants from the TiO₂ photocatalytic electrode, we employ an atmospheric-pressure O₂ plasma jet and the exposure time is controlled by the scanning rate. As the results, photodegradation efficiency of methylene blue is significantly enhanced with a scanning rate in the range of 100-500 μm/s and was saturated with a scanning rate in the range of 10-100 μm/s.     

Synthesis of cadmium sulfide‐reduced graphene oxide nanocomposites by pulsed laser ablation in liquid for the enhanced photocatalytic reactions in the visible light

The large‐scale applications of cadmium sulfide (CdS) nanoparticles (NPs) as a photo‐catalyst are limited by their poor stability (high aggregation tendency) and consequent reduction in the surface area and increased rate of recombination of photoinduced electron‐hole pairs, despite its inherent positive feature of being visible light active. It has been reported that the photocatalytic performance of CdS can be considerably improved if CdS is made as a composite material with reduced graphene oxide (rGO) in an optimum ratio. In this work, for the first time, we adopted the technique of pulsed laser ablation in liquids (PLAL) to synthesize highly pure CdS NPs and the required CdS/rGO nanocomposites using high purity (99.9%) microstructured CdS and graphene oxide as chemical precursors. PLAL is a simple and rapid 1‐step synthesis process (where the reaction time is reduced from several hours to a few minutes), which does not require high temperature, toxic chemicals, and the final treatment to remove the unwanted by‐products. The optical and morphological characterizations revealed that the anchoring of CdS on rGO transformed the CdS/rGO composite into an efficient photo‐catalyst by enhancing the following positive attributes required for a good photo‐catalyst: (1) The inherent tendency of aggregation of CdS is considerably reduced; CdS NPs with an average grain size of 20 nm are well placed on the rGO sheets; and hence, the surface area of the catalyst was significantly increased to provide more active sites. (2) The reduced rate of photoinduced electron‐hole recombination manifested in the photoluminescence spectrum indicated the effective charge separation. (3) The enhanced light absorption in the visible/infrared region ensured the effectiveness of this material in naturally abundant solar radiation. In the CdS/rGO composite, the rGO sheets play the role of a supporting matrix, cocatalyst, and electron acceptor for CdS. To evaluate the photo‐catalytic performance of CdS/rGO, we applied it as a visible light‐driven photo‐catalyst for degrading methylene blue dye and found that CdS/rGO nanocomposite was more efficient than pure CdS in the visible spectral region. Therefore, PLAL provides a simple and 1‐step route to synthesize high‐purity visible light–driven photo‐catalysts and solar cell material.     

UV/TiO_2光催化氧化工艺脱汞的试验研究

UV/TiO_2光催化技术在TiO_2催化剂的作用下可将烟气中Hg~0氧化脱除。利用自制的UV/TiO_2氧化试验台研究了影响Hg~0去除率的相关因素,结果表明,在无催化剂和有紫外灯情况下可脱除少量Hg~0;Hg~0去除率随催化剂活性组分含量的增加而上升,但上升速率逐渐下降;在温度(50～200)℃范围内,Hg~0去除率无明显变化;Hg~0去除率随着Hg~0初始浓度的升高逐渐下降;Hg~0去除率随着烟气中氧含量先上升后趋于不变。UV/TiO_2氧化工艺脱汞可为燃煤电厂烟气脱汞提供理论指导。     

Microbial coupled photocatalytic fuel cell with a double Z-scheme g-C3N4/ZnO/Bi4O5Br2 cathode for the degradation of different organic pollutants

A novel heterostructure of g-C₃N₄/ZnO/Bi₄O₅Br₂ (ZB-3) was designed, and used in the microbial coupled photocatalytic fuel cell (MPFC). It can effectively improve electron utilization efficiency and pollutant degradation using this double Z-scheme heterojunction structure. The current–time (I–t) curves demonstrated that the current density of ZB-3 was higher than that of ZnO, ZnO/Bi₄O₅Br₂ (ZB-1), g-C₃N₄/ZnO (ZB-2). Electrochemical impedance spectroscopy (EIS) indicated ZB-3 possessed the minimum charge-transfer resistance. This MPFC for degrading rhodamine B (RhB) and tetracycline (TC) under different conditions were developed using these materials. Even in the dark condition, MPFC with g-C₃N₄/ZnO/Bi₄O₅Br₂ demonstrated 93% and 82% degradation efficiency for RhB and TC, respectively. Furthermore, the electron transport mechanism of the MPFC and ZB-3 were proposed. It paves the approach for more efficient pollutant degradation via MFC photocatalysis.     

Enhanced UV- and visible-light driven photocatalytic performances and recycling properties of graphene oxide/ZnO hybrid layers

Light induced catalytic processes have attracted significant attention during the last years for wastewater treatment due to their efficiency in decomposition of organic contaminants. In this study we report the synthesis of graphene oxide (GO)/ZnO hybrid layers with high photocatalytic efficiency using laser radiation. The results show that the hybrid layers exhibit much improved photodecomposition efficiency as compared to pure GO or ZnO both under UV and visible-light irradiation. The enhanced photocatalytic efficiency of the hybrid as compared to the reference pure ZnO and GO layers was attributed to the contribution of GO to the separation and transport of the photogenerated charge carriers. Additionally, under visible light irradiation the organic molecules can act as first sensitizers in the degradation process. The recyclability of the layers was also investigated through repetitive photodegradation cycles under UV- or visible-light irradiation. After consecutive degradation runs, the hybrid photocatalyst layers were still stable and retained high degradation efficiency, ensuring reusability. The photocatalytic activity of the layers was correlated with the gradual change of their chemical structure during consecutive degradation cycles. Owing to the high photodegradation efficiency, reusability, and ease of recovery the synthesised hybrid layers consisting of easily available materials are suitable for environmental purification applications.