•MWCNTs/Fe3O4 composites were synthesized by a hydrothermal process.•MWCNTs/Fe3O4 magnetic composites with adsorption and catalytic ozonation performance for BPA.•MWCNTs/Fe3O4 showed enhanced activity due to hollow tube structure and surface oxygen-containing groups.•BPA removal efficiency could be promoted in co-existence of humic acid due to increased OH radicals.MWCNTs/Fe3O4 magnetic composites, combined adsorption and catalytic ozonation behavior, were synthesized by a hydrothermal process. The synthesized MWCNTs/Fe3O4 composites were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), element analysis and Brunauer-Emmett-Teller (BET) surface area. The adsorption performance and catalytic activity of MWCNTs/Fe3O4 for BPA removal in aqueous solution were evaluated. The results showed that the synthesized MWCNTs/Fe3O4 exhibited an excellent adsorption ability and catalytic ozonation activity owning to its large specific surface areas, hollow tube channels and abundant surface oxygen-containing groups, leading to high adsorption for BPA and O3, high retention and utilization of O3 molecules on the composites. In addition, the catalytic ozonation performance of MWCNTs/Fe3O4 could be improved by increasing surface oxygen-containing groups to accelerate O3 decomposition, thus producing more OH radicals. Moreover, BPA removal efficiency could be improved by increasing dose of catalyst, pH value and the concentration of humic acid (HA). The fluorescence spectra and OH radicals measurement displayed that HA could greatly increase OH radicals via inducing more surface oxygen-containing groups on the catalyst, thus, promoting BPA removal. Furthermore, MWCNTs/Fe3O4 showed the great stability and durability during several reaction recycles.Download high-res image (260KB)Download full-size image

•NTHPC is successfully synthesized via the MnO2-introduced-tunnels strategy.•The nanotunnels are successfully introduced into hierarchical-porous carbon.•NTHPC shows a higher specific surface area and moderate pore volume.•NTHPC displays excellent supercapacitive performance.•This work provides a novel way for preparing hierarchical-porous carbon materials.Nanotunnels inserted hierarchical-porous carbon (NTHPC) have been synthesized successfully via a MnO2-introduced-tunnels strategy using MnO2 nanorods as template, with agar and β-cyclodextrin serving as hybrid carbon precursors. The as-prepared NTHPC possesses a higher specific surface area of 1441 m2 g−1, a moderate pore volume of 1.23 cm3 g−1, and the hierarchical-porous structure with inserted nanotunnels. Transmission electron microscopy has demonstrated that the width of the nanotunnels is between 20 and 100 nm, and the length ranges from 0.2 to 2.0 μm. Tests in a three-electrode system showed that the NTHPC has high specific capacitance (253.1 F g−1, 5 mV s−1), as well as good rate capability (203.3 F g−1, 100 mV s−1) and excellent cycling stability. More importantly, an assembled symmetric supercapacitor with NTHPC electrodes delivered an outstanding energy density of up to 34.9 Wh kg−1 with power density of 755.2 W kg−1. The remarkable electrochemical performance of the NTHPC is ascribed to the nanotunnels, which act as ion reservoirs and liquid transfer channels that can increase the ion transport rate and shorten the ion transfer distance. This study provides a novel method for the preparation of high-performance hierarchical-porous carbon and guidance for its potential applications in supercapacitors.Download high-res image (276KB)Download full-size image

•A three-dimensional porous graphene layers was prepared via a gas foaming method.•Melamine was the nitrogen source to synthesize the N-doped 3D graphene layers.•The specific surface area of 3D N-doped graphene material is as high as 1196 m2 g−1.•The 3D N-doped graphene specific capacitance is 335 F g−1 in three-electrode system.•The energy density of 3D N-doped graphene reaches 58.1 Wh kg−1 in a symmetric cell.A porous graphene layers with a three-dimensional structure (3DG) was prepared via a gas foaming method based on a polymeric predecessor. This intimately interconnected 3DG structure not only significantly increases the specific surface area but also provides more channels to facilitate electron transport. In addition, 3D N-doped (3DNG) layers materials were synthesized using melamine as a nitrogen source. The nitrogen content in the 3DNG layers significantly influenced the electrochemical performance. The sample denoted as 3DNG-2 exhibited a specific capacitance of 335.2 F g−1 at a current density of 1 A g−1 in a three-electrode system. Additionally, 3DNG-2 exhibited excellent electrochemical performance in aqueous and organic electrolytes using a two-electrode symmetric cell. An energy density of 58.1 Wh kg−1 at a power density of 2500 W kg−1 was achieved, which is approximately 3 times that (19.6 Wh kg−1) in an aqueous electrolyte in a two-electrode system. After 1000 cycles, the capacity retention in aqueous electrolyte was more than 99.0%, and this retention in organic electrolytes was more than 89.4%, which demonstrated its excellent cycle stability. This performance makes 3DNG-2 a promising candidate as an electrode material in high-power and high-energy supercapacitor applications.

•Three-dimensional N-doped graphene hydrogels were synthesized using a hydrothermal method.•The hydrogels exhibited strong mechanical properties.•The synthesized NG-3:3 showed excellent capacitance (387.2 F g−1 at 1 A g−1).Three-dimensional nitrogen-doped graphene hydrogel (3D NG) samples are successfully synthesized via a hydrothermal method. The synthesized 3D NG exhibits excellent mechanical properties, including the support of approximately 1165 g with three NG cylinders. The morphology, structure, component and electrochemical performance of the NG samples are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscope, X-ray photoelectron spectroscopy, thermogravimetric analysis, N2 adsorption-desorption, cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy, respectively. X-ray photoelectron spectroscopy indicates that N is present in the graphene as pyrrolic N, pyridinic N and quaternary/graphitic N, with pyrrolic N being the predominant species in all of the samples. The electrochemical results demonstrate that the 3D NG with a nitrogen content of 7.7 wt% shows excellent capacitive behavior (387.2 F g−1 at 1 A g−1) in 6 M KOH. In addition, the specific capacitance value of this sample remains at approximately 90.5% of the maximum value (298.5 F g−1 at 5 A g−1) after 5500 cycles. The main reason for the excellent electrochemical behavior is the incorporation of the pyrrolic and pyridinic N in the graphene, enhancing the pseudo-capacitance of this material. It indicates that the 3D NG can be used as an electrode material for high-performance supercapacitors.

•RGO/CoAl-LDHs nanocomposites were prepared by a electrostatic self-assembly method.•Face-to-face contact between CoAl-LDHs and GO nanosheets can be observed from TEM.•The nanocomposite exhibited a higher specific capacitance and rated capability.•Self-agglomeration of the nanosheets can be avoided by electrostatic self-assembly.Graphene oxide/CoAl-layered double hydroxide (GO/CoAl-LDHs) composites were successfully prepared by a face-to-face electrostatic self-assembly method. Positively charged colloidal CoAl-LDHs nanosheets (CoAl-LDH-NS) and negatively charged colloidal GO nanosheets were uniformly mixed; then CoAl-LDH-NS were assembled on GO nanosheets via electrostatic attraction to prepare GO/CoAl-LDHs composites. The GO/CoAl-LDHs composites were then transformed to the reduced graphene oxide/CoAl-layered double hydroxide (RGO/CoAl-LDHs) composites with a hydrothermal method. The results showed that the content of RGO has a remarkable influence on the capacitive properties of composites. Among the composites with different RGO content, the RGO/CoAl-LDHs composite containing 12.0 wt% RGO displayed a maximum specific capacitance of 825 F g−1 at low current density of 1 A g−1, while that of pure CoAl-LDHs was 552 F g−1. The capacitance retention of the RGO/CoAl-LDHs composite from 1 A g−1 to 8 A g−1 is found to be 62.3%, whereas that of pure CoAl-LDHs is only 31.9%. Face-to-face self-assembling between positively charged CoAl-LDH-NS and negatively charged GO nanosheets can effectively reduce the self-agglomeration of GO nanosheets and avoid CoAl-LDH-NS stacking together, which lead to improvement of the capacitive performance.

Inspired by baking bread, our research group demonstrates a novel method for baking three-dimensional (3D) graphene layers with an open porous network, pore size in the range of dozens of nanometers to several hundred nanometers, and a pore wall thickness of about 10 nm. Such continuously cross-linking structures not only effectively overcome the restacking and agglomeration of graphene nanosheets but also possess more channels between nanosheets to lower the resistance for electron access to the inter-space. Compared with reduced graphene oxide (rGO) prepared at the same temperature, the unique 3D porous-structured graphene layers also contain 4.3 at.% nitrogen. When the 3D graphene layers are employed as an active electrode material for a supercapacitor, a high specific capacitance (SC) of 231.2 F g−1 at 1 A g−1 is displayed after electrochemical activation, approximately two times that of rGO. Only <1.0% of the capacitance degrades after 8000 cycles, exhibiting its excellent cycle stability; furthermore, it liberates a high energy density of 32.1 Wh kg−1 at a power density of 500 W kg−1. The attractive performances of 3D graphene layers make them a promising candidate as an electrode material for supercapacitors.

•The negative electrode sheets are prepared by simulating manufacture condition of negative plates.•The effect of carbon additives on negative electrode sheets is studied by electrochemical method.•Carbon additives in NAM enhance electrochemical properties of the negative sheets.•The negative sheets with 0.5 wt% carbon additive exhibit better electrochemical performance.•The charge-discharge mechanism is discussed in detail according to the experimental results.In this study, carbon additives such as activated carbon (AC) and carbon black (CB) are introduced to the negative electrode to improve its electrochemical performance, the negative electrode sheets are prepared by simulating the negative plate manufacturing process of lead-acid battery, the types and contents of carbon additives in the negative electrode sheets are investigated in detail for the application of lead-carbon battery. The electrochemical performance of negative electrode sheets are measured by chronopotentiometry, galvanostatic charge-discharge and electrochemical impedance spectroscopy, the crystal structure and morphology are characterized by X-ray diffraction and scanning electron microscopy, respectively. The experimental results indicate that the appropriate addition of AC or CB can enhance the discharge capacity and prolong the cycle life of negative electrode sheets under high-rate partial-state-of-charge conditions, AC additive exerts more obvious effect than CB additive, the optimum contents for the best electrochemical performance of the negative electrode sheets are determined as 0.5wt% for both AC and CB. The reaction mechanism of the electrochemical process is also discussed in this paper, the appropriate addition of AC or CB in negative electrode can promote the conversion of PbSO4 to Pb, suppress the sulfation of negative electrode sheets and reduce the electrochemical reaction resistance.

•The G/MnO2 composites were prepared by an electrostatic self-assembly method.•The graphene was obtained by an electrochemical exfoliation method.•Opposite charges were preconditions for the electrostatic self-assembly process.•The face-to-face contact style improved effectively the conductivity of MnO2.•95.6% of maximum capacitance was retained after 10000 cycles in the G-2/MnO2.Layered graphene/manganese oxide (G/MnO2) nanocomposites for supercapacitor applications were prepared with a face-to-face electrostatic self-assembly method using high-quality graphene, which was obtained from the one-step electrochemical exfoliation of graphite. The results reveal that the graphene and MnO2 nanaosheets need to be oppositely charged for the electrostatic self-assembly process. The face-to-face contact between the MnO2 nanosheets and graphene can effectively improve the conductivity of MnO2 and prevent the restacking and agglomeration of graphene. In addition, the composites exhibit an electrochemical-activation behavior, and the ratio of MnO2/graphene in composites significantly influences the electrochemical performance. The G-2/MnO2 composite displays a specific capacitance of 319 F g−1 at 0.2 A g−1, and only 4.4% of the capacitance degrades after 10,000 cycles, which demonstrates the composite's excellent cycle stability. Furthermore, the composite features a high energy density of 31.5 Wh kg−1 at a power density of 100 W kg−1. This attractive performance makes it a promising candidate as an electrode material for supercapacitors. Remarkably, although the graphene content in G-4/MnO2 composite is the same, the specific capacitance reduced to 186 F g−1 due to the different mixing times.

•Vanadium oxynitride-carbon (VOxNy-C) materials were prepared by soft-template method.•The maximum specific capacitance (SC) of VOxNy-C is 271 Fg−1 at 1 Ag−1•The SC of VOxNy-C lost less than 10% as the scan rate increases from 5 to 100 mV s−1•Restricting the potential window can increase the cycling stability of VOxNy-C.By using Polyvinylpyrrolidone (PVP) as the soft-template, vanadium oxynitride-carbon (VOxNy-C) nanomaterials were synthesized by NH3 reduction of V2O5 xerogel. The powder X-ray diffraction result indicated that the VOxNy-C belongs to the cubic crystal system. Transmission electron microscopy (TEM) images showed that most of the VOxNy grains in VOxNy-C materials were lower than 20 nm. Electrochemical test results showed that VOxNy-C materials exhibited better conductivity and enhanced electrochemical properties compared to VOxNy materials which were synthesized only by NH3 reduction of V2O5 xerogel. The maximum specific capacitance of VOxNy-C electrode reaches up to 271 Fg−1 at 1 Ag−1 which is much higher than that of VOxNy electrode (143 F g−1). The specific capacitance of VOxNy-C electrode lost less than 10% as the scan rate increased 20 times from 5 to 100 mV s−1, showing its superior rate capability. The VOxNy grains and remaining carbon were intimate contact each other in VOxNy-C nanocomposite which results in a better electronic conductivity, as well as the high surface area which furnishes more surface active redox sites of VOxNy-C nanocomposite. Therefore, VOxNy-C material exhibited better electrochemical performance than VOxNy. Cycle tests showed that restricting the potential window can improve the cycling stability of the VOxNy-C electrode. This cycle phenomenon may be ascribed to the use of high upper potentials which lead to the irreversible oxidation of electrode materials and the concomitant formation of soluble vanadium based species, which further result in the reduction of the active redox sites, and ultimately enhance the electrode's irreversibility in 1 M KOH.

•ZVI-mediated advanced oxidation was applied to degrade acid orange II (AOII).•Lower pH in aqueous media was favorable for AOII degradation in ZVI/O2 system.•The measurement of H2O2 and Fe2+ demonstrated role of Fenton reaction in ZVI/O2 system at low pH.•OH produced via Fenton reaction was reactive species to degrade AOII in ZVI/O2 system.In this study, zero-valent iron (ZVI)-mediated advanced oxidation was applied to degrade the acid orange II (AOII) in the presence of oxygen. The effect of pH value, ZVI dosage, O2 concentration and added Fe2+ ions on the degradation efficiency was investigated. It was found that the increases of acidity in aqueous solution, ZVI dosage and O2 concentration were favorable to the oxidation reaction of AOII in ZVI-mediated advanced oxidation processes. The lower pH value in aqueous medium was favorable for AOII degradation in ZVI/O2 system. The AOII degradation efficiency and COD removal efficiency system could achieve more than 95% and 65% within 3 h in the ZVI/O2 at initial pH 3.0, respectively. The AOII degradation in ZVI/O2 system followed the first-order reaction kinetics at pH range of 3.0–7.0, while AOII degradation followed the zero-order reaction kinetics at pH range of 9.0–11.0. The measurements of H2O2 and Fe2+ in ZVI/O2 system, and the characterization for used ZVI particles demonstrated the role of Fenton reaction in the ZVI/O2 system, which occurred favorably at low pH to generate H2O2 and Fe2+, followed by a likely species OH to degrade AOII. The involvement of OH in oxidizing AOII was examined by determining the degradation rates using OH scavenger. Moreover, the coexistence ions had no significantly influence the oxidation process, indicating the true application process. Finally, organic compounds as intermediates of the degradation process were identified by LC/MS.

•TMA+ intercalated MnO2 was synthesized via an exfoliation and self-assembly process.•The as-prepared self-assembled MnO2 exhibits an ordered layered structure.•The as-prepared MnO2 possesses a large interlayer spacing of 0.67 nm.•The maximum specific capacitance of self-assembled MnO2 is 180 F g−1 at 0.5 A g−1.•The specific capacitance of self-assembled MnO2 decreased 10% after 10,000 cycles.Layered birnessite-type manganese oxide is exfoliated into single-layer manganese oxide nanosheets. Then, the exfoliated manganese oxide nanosheets are spontaneously restacked by a self-assembly process, which is driven mainly by electrostatic interactions between the negatively charged manganese oxide nanosheets and the positively charged tetramethylammonium (TMA+) ions, yielding a new ordered layered structure of MnO2 (self-assembled MnO2) with a large interlayer spacing of 0.67 nm, suggesting the formation of a layered hybrid form, intercalated with TMA+ ions in residence between the manganese oxide nanosheets. The large interlayer spacing facilitates rapid ion exchange and the intercalation and deintercalation of electrolyte cations. The supercapacitive behavior of the as-prepared self-assembled MnO2 is evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge (CD) experiments and electrochemical impedance spectroscopy (EIS). The specific capacitance value is 180 F g−1 at a current density of 0.5 A g−1. After 10,000 cycles, the specific capacitance is still approximately 90% of the maximum specific capacitance. In addition, the intercalation of TMA+ ions between the manganese oxide nanosheets leads to a low charge-transfer resistance. These experimental results demonstrate that this self-assembled MnO2 is a promising candidate for use as electrode material in supercapacitor applications.

•Simultaneous separation of AO7 degradation product using newly developed CE-C4D technique.•Developed CE-C4D technique is simple, fast, and sensitive.•CE-C4D technique has potential for in-situ monitoring of target compounds•Degradation of AO7 by Fenton reagent to six compounds.Capillary electrophoresis (CE) with capacitively coupled contactless conductivity detector (C4D) was developed to separate azo-dyestuff acid orange 7 (AO7) and its six degradation products. The analyzed products were sulfamic acid, oxalic acid, benzenesulfonic acid, 4-hydroxybenzene sulfonic acid, phthalic acid, and 4-aminobenzene sulfonic acid. In developing the method, types and concentrations of running buffers, injecting voltage and time, and applied voltage were tested to obtain optimum conditions to analyze target compounds. The separation was successfully achieved within 10 min using a fused-silica capillary under the following conditions: 20 mmol L−1 acetate acid buffer, electrokinetic injection of −12 kV×10 s, and applied voltage of −13 kV. The developed method was applied to analyze degradation products in situ during the reaction of AO7 with Fenton reagent (FeII+H2O2 at pH 4.0).

A hydration-layered structure of buserite-type manganese oxide (Mg–buserite) was successfully synthesized by an ion exchange method. The as-prepared Mg–buserite possesses a large basal spacing of 10 Å, and contains Mg2+ ions and two sheets of water molecules in the interlayer region. The supercapacitive behaviors of Mg–buserite were systematically investigated by cyclic voltammetry (CV), galvanostatic charge–discharge (CD) experiments and electrochemical impedance spectroscopy (EIS). The results showed that the specific capacitance of the Mg–buserite electrode sharply increased during the initial 500 cycles and reached a maximum of 164 F g−1 at approximately the 500th cycle at a scan rate of 1 mV s−1, and then it remained an almost constant value and decreased slightly upon prolonged cycling. After 22,000 cycles, the specific capacitance decreased by approximately 6% of the maximum specific capacitance. The superior capacitive behavior and excellent cycling stability of the as-prepared Mg–buserite are attributed to the large basal spacing, which can accommodate a larger amount of electrolyte cations and provide more favorable pathways for electrolyte cations intercalation and deintercalation. The experimental results demonstrate that Mg–buserite is a promising candidate as an electrode material for supercapacitors.Highlights► Mg–buserite with a large basal spacing of 10 Å was successfully synthesized. ► Mg2+ and two sheets of H2O molecules occupy the interlayer region of Mg–buserite. ► The maximum specific capacitance of Mg–buserite is 164 F g−1 at 1 mV s−1. ► The specific capacitance of Mg–buserite decreased only 6% after 22,000 cycles. ► The superior capacitive behaviors are attributed to the large basal spacing.

A todorokite-type manganese oxide (T-MnOx) with a 3 × 3 large tunnel structure was successfully synthesized by a hydrothermal method and employed as an active electrode material for a supercapacitor. The todorokite structure of the as-prepared manganese oxide was confirmed by X-ray diffraction (XRD), and the fragmented platelets were observed by scanning electron microscopy (SEM). The electrochemical performances of the as-prepared T-MnOx were evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge (CD) experiments and electrochemical impedance spectroscopy (EIS) in 1 M Na2SO4 electrolyte. The specific capacitance of the T-MnOx electrode sharply increased during the initial 1000 cycles and then continued improving gradually. It reached a maximum of 220 F g−1 at approximately the 4000th cycle at a scan rate of 2 mV s−1, and further studies showed that the morphology and structure of the T-MnOx were maintained after 4000 cycles, indicating that an electrochemical activation process occurred during the initial thousands of cycles. The electrochemical activation mechanism is discussed in detail. The specific capacitance remained an almost constant value and decreased slightly upon prolonged cycling. After 23,000 cycles, it decreased by 6% of the maximum specific capacitance. The experimental results demonstrate that T-MnOx is a promising candidate as an electrode material for supercapacitors.Highlights► The electrochemical capacitance behavior of todorokite (T-MnOx) was studied. ► The T-MnOx with 3 × 3 large tunnels was successfully synthesized. ► The maximum specific capacitance of the T-MnOx electrode is 220 F g−1 at 2 mV s−1. ► The as-prepared T-MnOx exhibits excellent cycle stability. ► The electrochemical activation mechanism is discussed in detail.

In this study, an effective photocatalytic disinfection of E. coli 8099 using Ag/BiOI composites under visible light irradiation (λ > 420 nm) was studied. The nanostructured Ag/BiOI composites were synthesized in the presence of ethylene glycol by a solvothermal process and subsequent photodeposition method. The prepared Ag/BiOI photocatalysts were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), energy dispersive spectrometer (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectra (DRS) measurement. The experimental results showed that the photocatalytic disinfection efficiency of E. coli (∼5 × 107 cfu mL−1) using 2.09%Ag/BiOI was almost 99.99% within 10 min irradiation, and significantly higher than that of BiOI. The determination of cell structure destruction by TEM microscopy and the measurement of released K+ further confirmed that the cell membranes of E. coli were ruptured in the photocatalytic disinfection. It was found that the deposited Ag can facilitate the surface-adsorbed O2 to scavenge the photogenerated electrons. The main active species OH for the photocatalytic disinfection performance of E. coli   was produced by two pathways, that is, hvb+ oxidized water molecules to form OH (oxidative pathway), and O2 captured the photogenerated electron to generate O2- and subsequently produce OH (reductive pathway).Highlights► Photocatalytic disinfection of E. coli using Ag/BiOI under visible light was studied. ► Ag/BiOI had a higher photocatalytic disinfection activity than BiOI under visible light. ► Deposited Ag can facilitate surface-adsorbed O2 to scavenge photogenerated electrons. ► OH was the reactive species for photocatalytic disinfection performance of E. coli.

The objective of this work was to develop a novel wet-scrubbing process using Fe(VI) for the simultaneous removal of gaseous NO and SO2. The oxidation of SO2 and NO with Fe(VI) was studied in aqueous solution at alkaline pH (9.0–11.0). A stoichiometric molar ratio for NO and SO2 oxidation with Fe(VI) was determined to be nearly 3.0. Sulfate and nitrate was identified as final products by ion chromatography from the reaction at pH 9.0–11.0. The feasibility of simultaneous removal of multiple gas pollutants with the continuous feeding of ferrate in lab-scale was investigated from the view of industrial application. It was found that the removal efficiency of NO and SO2 was enhanced with the increase of Fe(VI) concentration, more than 90% NO removal efficiency and 100% SO2 removal efficiency were achieved by wet-scrubbing process using Fe(VI) at room temperature and ambient atmosphere. The results demonstrate that Fe(VI) could be an effective wet-scrubbing agent for the simultaneous removal of NO and SO2.

The catalytic activities of carbon-based AgBr nanocomposites (AgBr/CNT, AgBr/GP, AgBr/EG, and AgBr/AC) for CO2 reduction to hydrocarbons under visible light were investigated in this study. The carbon-based AgBr nanocomposites were prepared on carbon-based supporting materials (CNT, GP, EG, and AC) by the deposition–precipitation method in the presence of cetyltrimethylammonium bromide (CTAB). The photocatalytic activities of AgBr nanocomposites on different supporting materials (CNT, GP, EG, and AC) were investigated by CO2 reduction yield in the presence of water under visible light (λ > 420 nm). The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that AgBr nanoparticles were well dispersed on the surface of supporting materials. AgBr/CNT and AgBr/GP had a relatively higher reduction yield under visible light due to the transfer of photoexcited electrons from the conduction band of well-dispersed AgBr to carbon supporting materials. In addition, the carbon-based AgBr nanocomposites were stable in the repeated uses under visible light. The total product yields of carbon-based AgBr nanocomposites after the 5 repeated uses almost remained about 83% of the first run. Therefore, carbon-based AgBr nanocomposite is an effective and stable visible-light-driven photocatalyst for CO2 photoreduction.

•3D MnO2 porous hollow microspheres (PHMSs) are prepared by a self-template process.•MnO2 PHMSs with excellent adsorption and catalytic ozonation performance for BPA.•MnO2 PHMSs show enhanced activity due to hollow-mesoporous shell spherical structure.•O2− and OH are reactive species to induce effective catalytic ozonation of BPA.Three-dimensional (3D) MnO2 porous hollow microspheres (δ- and α- MnO2 PHMSs), with high adsorption and catalytic ozonation performance, were synthesized by a self-template (MnCO3 microspheres) process at room temperature. The synthesized MnO2 PHMSs were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) surface area. The results showed that PHMSs exhibit the excellent adsorption ability and catalytic activity owning to their hollow spherical structure, mesoporous shell and well-defined interior voids, leading to the strong adsorption for bisphenol A (BPA) and the retention of O3 molecules on catalyst. Moreover, the catalytic performance of α-MnO2 PHMSs was better than that of δ-MnO2 PHMSs which was attributed to the richer lattice oxygen of α-MnO2 PHMSs to accelerate O3 decomposition by producing more reactive oxidative species. The degradation efficiency of BPA using 3D α-MnO2 PHMSs was more than 90% in the presence of ozone within 30 min reaction time. The probe tests for reactive oxidative species (ROSs) displayed that BPA degradation by catalytic ozonation is dominated by O2− and OH in our present study. Furthermore, the organic compounds as intermediates of the degradation process were identified by LC/MS.Download high-res image (129KB)Download full-size image

Urgent development of effective and low-cost technologies for reduction CO2 is needed to address global warming caused by atmospheric CO2 and the depletion of fossil fuels. In this investigation, an effective photocatalytic reduction of CO2 using AgBr/TiO2 photocatalyst under visible light (λ > 420 nm) was studied. The nanostructured AgBr/TiO2 photocatalyst was prepared by the deposition-precipitation method in the presence of cetyltrimethylammonium bromide (CTAB), and characterized by X-ray diffraction (XRD), diffuse reflectance spectra (DRS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Their photocatalytic activities were evaluated by the reduction yield in the presence of CO2 and water. The experiment results showed that 23.2% AgBr/TiO2 had relatively high reduction yields under visible-light irradiation for 5 h, with a methane yield of 128.56, methanol yield of 77.87, ethanol yield of 13.28, and CO yield of 32.14 μmol g−1, respectively. The highly efficiently photocatalytic activities of AgBr/TiO2 in the reduction process of CO2 is attributed to its strong absorption in the visible-light region. In addition, it was found that AgBr/TiO2 photocatalyst was stable in the repeated uses under visible light irradiation, due to the transfer of photoexcited electrons from the conduction band of well-dispersed AgBr to that of TiO2.Graphical abstractDownload high-res image (123KB)Download full-size imageHighlights► A direct contact between AgBr and TiO2 leads to the enhanced photocatalytic activity. ► AgBr/TiO2 is an effective visible-light-driven photocatalyst for CO2 photoreduction. ► Extended absorbance of AgBr/TiO2 promotes CO2 photoreduction under visible light. ► The transfer of excited electrons from AgBr to TiO2 leads to the stability of AgBr.

Ag/BiOI composites were synthesized by a solvothermal process and subsequent photodeposition method. The prepared Ag/BiOI photocatalysts were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), energy dispersive spectrometer (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectra (DRS) measurement. The experimental results showed that the photocatalytic disinfection efficiency of E. coli using visible-light-driven Ag/BiOI was almost 99.99%, and significantly higher than that of BiOI. The determination of of released K+ further confirmed that the cell membranes of E. coli were ruptured in the photocatalytic disinfection.

The objective of this work was to develop a novel wet-scrubbing process using Fe(VI) for the simultaneous removal of gaseous NO and SO2. The oxidation of SO2 and NO with Fe(VI) was studied in aqueous solution at alkaline pH (9.0–11.0). A stoichiometric molar ratio for NO and SO2 oxidation with Fe(VI) was determined to be nearly 3.0. Sulfate and nitrate was identified as final products by ion chromatography from the reaction at pH 9.0–11.0. The feasibility of simultaneous removal of multiple gas pollutants with the continuous feeding of ferrate in lab-scale was investigated from the view of industrial application. It was found that the removal efficiency of NO and SO2 was enhanced with the increase of Fe(VI) concentration, more than 90% NO removal efficiency and 100% SO2 removal efficiency were achieved by wet-scrubbing process using Fe(VI) at room temperature and ambient atmosphere. The results demonstrate that Fe(VI) could be an effective wet-scrubbing agent for the simultaneous removal of NO and SO2.