•A novel AgI/Ag2CO3 heterojunction was prepared via coprecipitation process.•AgI/Ag2CO3 heterojunction increase e−/h+ pairs separation.•The production of •OH and O2•− radicals was promoted.•High ...photocatalytic activity and stability were obtained over AgI/Ag2CO3.
An insurmountable problem for silver-based semiconductor photocatalysts is their poor stability. Here, at room temperature, AgI with different concentrations (5%, 10%, 20% and 30%) were coupled into Ag2CO3, producing a series of novel AgI/Ag2CO3 composite photocatalysts. The effects of AgI addition on the Ag2CO3 catalyst for photocatalytic degradation of methyl orange (MO) under visible light irradiation have been investigated. Some physicochemical technologies like N2 physical adsorption/desorption, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectroscopy (UV–vis DRS) were applied to characterize these products. Results show that the photocatalytic degradation activity of AgI/Ag2CO3 photocatalyst is much higher than that of pure AgI and Ag2CO3. With the optimal content of AgI (20wt%), the AgI/Ag2CO3 exhibits the highest photocatalytic degradation efficiency. Its first order reaction rate constant (0.54h−1) is 20 times of that of AgI (0.026h−1) and 3.6 times of that of Ag2CO3 (0.15h−1). The characterizations and theory calculation show that AgI and Ag2CO3 have suitably matched band gap structures. The formation of AgI/Ag2CO3 heterojunction with intimate interface could effectively increase the separation efficiency of the e−/h+ pairs and promote the production of •OH and O2•− radicals, which brings about the fast degradation rate of the dye and an increase in photocatalytic stability.
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► Novel PbWO4 microspheres with hierarchical nanostructures were synthesized. ► The morphology and photocatalytic performance of PbWO4 crystals were controlled by pH value in ...preparation. ► PbWO4 microspheres exhibited remarkable photocatalytic activity and stability. ► Hierarchical structures and low recombination rate of the e−/h+ pairs enhanced photocatalytic performance.
Novel PbWO4 crystals with different morphologies, 14-faceted polyhedrons, hierarchical microspheres and nanoparticles, were fabricated by adjusting pH value under hydrothermal conditions. The as-prepared PbWO4 samples were characterized by nitrogen-physical adsorption, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–vis diffuse reflectance spectra, photoluminescence emission spectroscopy, and Fourier transform infrared spectroscopy. The photocatalytic performance of the PbWO4 crystals with different nanostructures in degradation of the acid orange II dye under UV light (365nm) was investigated. The plausible growth mechanisms for PbWO4 crystals with different morphologies were proposed. Photocatalytic tests showed that the performance of PbWO4 crystals strongly depended on their morphologies. PbWO4 microspheres with hierarchical nanostructures prepared under pH 7.0 at 140°C exhibited the highest activity and stability in recycling reaction. The degradation kinetics of dye over PbWO4 crystals was found to conform to the pseudo-first order model. The enhanced photocatalytic performance was attributed to the unique hierarchical nanostructures with high surface area and improved surface properties. Moreover, the high crystallinity of PbWO4 microspheres exhibited an enhanced catalytic activity owing to lower recombination rate of photo-generated electron/hole pairs. These novel hierarchical PbWO4 microspheres hold promise in applications of environmental purification.
A green low-cost redox flow battery using Zn/Zn2+ redox couple in HAc/NaAc medium and Fe2+/Fe3+ redox couple in H2SO4 medium was first proposed and investigated for potential stationary energy ...storage applications. The presence of HAc/NaAc in the negative electrolyte can keep the pH between 2.0 and 6.0even when a large amount of H+ ions move into negative electrolyte from positive electrolyte through ion exchange membrane. In the pH range of 2.0–6.0, the chemical reaction of Zn species with H+ species is very insignificant; furthermore, the electroreduction of H+ ion on the negative electrode is significantly suppressed at this pH range. The zinc-ferrum redox flow battery（Zn/Fe RFB） operated within a voltage window of 0.5–2.0 V with a nearly 90% utilization ratio, and its energy efficiency is around 71.1% at room temperature. These results show that Zn/Fe RFB is a promising option as a stationary energy storage equipment.
An ultrasonic method was developed to fabricate novel mesoporous TiO2 nanocrystals doped with a high concentration of N (N/TiO2). The nanocrystals were characterized by physicochemical methods ...including N2 physical adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, and UV-Vis diffuse reflectance spectroscopy. The photocatalytic degradation of dimethyl phthalate, a hazardous chemical in water, by the prepared N/TiO2 nanocrystals under visible light irradiation (400–660 nm) was investigated. The results show that N-doping efficiency under ultrasonic irradiation is 3.2 times higher than under typical conditions, and the produced TiO2 nanocrystals have mesoporous structure. N/TiO2 fabricated under ultrasound exhibited much higher efficiency for the degradation of dimethyl phthalate than that prepared under typical conditions. The high photocatalytic degradation activity of N/TiO2 fabricated under ultrasound is mainly attributed to its high N content effectively increasing its ability to absorb visible light.
采用超声波辐射法制备了具有介孔结构的高浓度氮掺杂TiO2纳米晶(N/TiO2). 采用N2物理吸附/X射线粉末衍射/X射线光电子能谱/透射电镜/光致发光谱和紫外-可见漫反射光谱等手段对N/TiO2进行了表征. 以波长为400–660 nm的可见光为光源, 以水体污染物邻苯二甲酸二甲酯为降解对象, 考察了不同制备方法对N/TiO2光催化性能的影响. 结果表明, 超声波辐射使氮掺杂浓度提高了2.2倍, 该法制备的N/TiO2同时具有较好的介孔结构, 表现了更高的光催化降解邻苯二甲酸二甲酯的活性. 其活性提高的主要原因是N/TiO2含有更高浓度的氮和对可见光具有更强的吸收能力.
An ultrasonic method was developed to fabricate mesoporous TiO2 nanocrystals doped with high concentration of N. N doping causes strong visible light absorption and high photocatalytic activity towards degradation of dimethyl phthalate under visible light irradiation.
Trace Ag2CO3 (0.5%, 1%, 2%, and 4%) was loaded on commercial TiO2 crystals by a facile precipitation method. The obtained Ag2CO3/TiO2 composites were characterized by X-ray diffraction (XRD), ...scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), photolimunescence (PL) spectroscopy, and UV–vis diffuse reflectance spectroscopy (DRS). Under UV light (λ = 254 nm) or visible light irradiation, the photocatalytic performance of the samples was tested in degradation of methyl orange (MO). Results showed that loading of 1 wt % Ag2CO3 results in the best photocatalytic activity. Under UV or visible light irradiation, the degradation activity of 1%Ag2CO3/TiO2 composite is 6 times that of TiO2 and 4 times that of Ag2CO3 or 3.4 times that of TiO2 and 1.7 times that of Ag2CO3. Reasons for enhanced activity were found that the coupling of Ag2CO3 promoted the visible light absorption and suppressed the recombination rate of e–/h+ pairs. Moreover, more surface OH groups over the Ag2CO3/TiO2 composite can react with the photogenerated h+ and produce •OH radicals to decompose the dye.
A series of novel Pt/BiOCl nanoplate photocatalysts were synthesized by a photodeposition method. The as-synthesized products were characterized by N sub(2) physical adsorption, X-ray diffraction, ...scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence (PL) emission spectroscopy, and UV-Vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the samples was evaluated by photocatalytic degradation of acid orange II under both UV light ( lambda = 254 nm) and visible light irradiation. The N sub(2) physical adsorption test showed that the deposition of Pt nanoparticles could not produce obvious change in the specific surface area of the catalyst. The UV-Vis DRS results indicated that the presence of Pt nanoparticles could effectively increase the visible light absorption ability of Pt/BiOCl. The PL spectra indicated that Pt could effectively suppress the recombination of photogenerated hole-electron pairs of Pt/BiOCl. Activity tests showed that the deposition of Pt (1%-2%, mass fraction) greatly promotes the UV right photocatalytic activity. Pt also brought about an obvious visible light activity, which could be attributed to the visible light absorption and plasmon photocatalysis role of deposited Pt nanoparticles.
► Novel F doped square-shaped TiO2 nanocrystals were fabricated using sonochemical method. ► Mesoporous structure was induced by ultrasound-induced aggregation effect. ► The photocatalytic properties ...were studied by phenol degradation. ► F doped TiO2 nano-squares show superior photocatalytic activity.
A sonochemical method was developed for the fabrication of novel square-shaped TiO2 nanocrystals doped with different F contents. The prepared samples were characterized by some physicochemical characterizations like X-ray diffraction (XRD), N2 physical adsorption, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrum (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy and UV–vis diffuse reflectance spectra (DRS). Phenol, as a hazardous chemical in water, was chosen to evaluate the photocatalytic degradation performance of the prepared TiO2 nanocrystals under UV light irradiation. Results show that under ultrasonic irradiation conditions, F can easily be doped into TiO2 and the obtained pure and F doped TiO2 nanocrystals show mesoporous structures which were formed by the role of ultrasound-induced aggregation. Moreover, the doping of optimal content of F (1.3mol%) gives 5.3 times increase in the phenol degradation rate. The high photocatalytic degradation activity of the doped TiO2 could be attributed to the factor that F doping increases the surface hydroxyl groups over TiO2 and effectively reduces the recombination rate of photo-generated electron/hole pairs, then producing more OH radicals to decompose the phenol molecules.
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•1.5–2μm hierarchical Pt/Bi2WO6 composite microflowers.•Pt NPs suppress the recombination of e−/h+ pairs and promote OH radicals production.•Superior texture properties of Pt/Bi2WO6 ...microflowers benefit their separation and recycle.•High visible light photocatalytic activity and stability were obtained over Pt/Bi2WO6.
A series of 1.5–2μm Pt/Bi2WO6 composite microflowers (mass concentration: 0.5%Pt, 1%Pt, 2%Pt, 4%Pt) assembled by Bi2WO6 nanosquares were synthesized by a hydrothermal synthesis combination with photo-deposition method. The as-synthesized microflowers were investigated by photocatalytic reaction and characterized by powder X-ray diffraction (XRD), N2-physical adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR). The results showed that these hierarchical Pt/Bi2WO6 composite microflowers have superior texture property in aqueous photocatalytic reactions. Moreover, the deposited Pt nanoparticles (NPs) play an important role in promoting the photocatalytic performance in degradation of acid orange II under visible light (λ>420nm) irradiation. The deposition of optimal amount of 1%Pt brings about 2.8 times increase in activity. The deposited Pt NPs over Bi2WO6 nanosquares enhance the visible light absorption, decrease the recombination rate of e−/h+ pairs and promote OH radicals production, hence largely boosting the photocatalytic activity. Moreover, the unique hierarchical structures of Pt/Bi2WO6 microflowers benefit their separation and recycle in aqueous photocatalytic reactions.
► Novel Ag/TiO2-B nanosquares were synthesized by a mild solvothermal method. ► Boron doping results in a substantial red-shift of the light absorption. ► Ag/TiO2-B showed high visible light ...photocatalytic efficiency in dye degradation. ► The synergistic effect of B doping and plasmon photocatalysis of Ag were observed.
Square-like B doped TiO2 nanocrystals were first synthesized by a mild solvothermal method with H3BO4 and titanium isopropoxide as the precursors, and isopropyl alcohol as reaction medium. Then, Ag nanoparticles were deposited on TiO2-B nanosquares by photo-deposition. The as-synthesized products have been investigated by photocatalytic reaction test and characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectra (DRS). The results showed that boron was successfully doped into TiO2 nanosquares under solvothermal condition. The obtained Ag/TiO2-B composite showed high efficiency in degradation of acid orange II under visible light irradiation. The high photocatalytic performance could be attributed to the synergistic effect of B doping and the plasmon photocatalysis role of the deposited silver nanoparticles over TiO2.
The paper first reports the use of a kind of positive electrode material (graphite/graphene-oxide composite) in zinc-cerium redox flow battery (RFB). It exhibits excellent electrochemical performance ...toward Ce
3+
/Ce
4+
redox couple in zinc-cerium RFB. The material was characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The electrochemical activity of this kind of material to Ce
3+
/Ce
4+
redox reaction was studied with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the electrochemical performance of the electrode was improved significantly when 2.5 wt% graphene oxide (GO) was added into graphite electrode. The redox peak current of Ce
3+
/Ce
4+
couple on the composite electrode was significantly larger than that on the graphite electrode, and the charge transfer resistance on the composite electrode is also obviously reduced. The enhanced electrochemical activity could be attributed to the presence of plentiful oxygen-containing functional groups on the basal planes and sheet edges of the GO and large specific areas introduced by the GO. The energy efficiency of zinc-cerium RFB using graphite/GO composite as positive electrode is around 76.3 %, which is larger than that using graphite (65.9 %). The excellent results demonstrate that the graphite/GO composite holds great promise in the application of zinc-cerium RFB.
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