Bo Chai

Enhanced visible light photocatalytic activity of BiOI/BiOCOOH composites synthesized via ion exchange strategy

The BiOI/BiOCOOH composites were synthesized by a facile ion exchange strategy between BiOCOOH precursor and KI by ultrasonic reaction. The as-prepared BiOI/BiOCOOH composites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance absorption spectra (DRS), Fourier transform infrared spectroscopy (FTIR) and photoluminescence spectra (PL). Under visible light illumination, the BiOI/BiOCOOH composites exhibited much higher photocatalytic activities than those of single BiOCOOH and BiOI for the degradation of Rhodamine B (RhB). The markedly enhanced photocatalytic activities of BiOI/BiOCOOH composites were attributed to the formation of a p–n heterojunction between p-type BiOI and n-type BiOCOOH, which facilitated the charge separation of photogenerated electron–hole pairs. The photoelectrochemical measurement confirmed that the charge separation efficiency was greatly improved by the formation of the heterojunction structure. Moreover, tests of radical scavengers demonstrated that h+ and ˙O2− were the main active species for the degradation of RhB.

The electrocatalytic activity of IrO2–Ta2O5 anode materials and electrolyzed oxidizing water preparation and sterilization effect

Ti/IrO2–Ta2O5 anode electrocatalysts with different contents and preparation temperatures were prepared by thermal decomposition in this work. The crystallite characterization and morphology were examined via XRD and SEM. The electrochemical properties were examined via cyclic voltammetry (CV) in 0.5 M H2SO4 and linear sweep voltammetry (LSV) in saturated sodium chloride. Through the study of different series of Ti/IrO2–Ta2O5 anodes, we find that the preparation conditions have a great impact on the electrode catalytic activity. Experimental results indicate that the electrochemically active surface area is determined by the content and morphology of the anode coating. When the IrO2 content and the preparation temperature are 70% and 500 °C, the surface of the electrode is aggregated with segregated crystallite flower-like particles, which brings about the best electrode catalytic activity. The current density in the chlorine evolution reaction of IrO2–Ta2O5 (70% and 500 °C) is 0.4 A cm−2 in saturated sodium chloride. The properties and sterilization effect of EO water are closely related to the electrode catalytic activity. The higher the current density is in chlorine evolution, the higher the available chlorine and HClO content. When the IrO2 content is 70% and the preparation temperature is 500 °C, the maximum values of the killing logarithm value and killing rate are 3.01–3.05 and 99.9023–99.9109%, respectively. In addition, when the Ti substrate undergoes 40 minutes of activation treatment, the Ti/IrO2–Ta2O5 anodes have the highest stability.

High-efficiency electrochemical hydrogen evolution based on the intermetallic Pt2Si compound prepared by magnetron-sputtering

The development of highly active and stable electrocatalysts for the hydrogen evolution reaction (HER) is central to the area of renewable energy. Si nanocomposites exhibited high efficiency in a light-induced hydrogen evolution reaction. However, there are few reports on the experimental application of the electrochemical HER. Herein, we report a simple synthesis of an intermetallic Pt2Si electrode using magnetron sputtering (MS) synthesis. The physical and electrochemical characterization of the materials was achieved by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray fluorescence (XRF), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Herein, the electrochemical catalytic activity towards the HER of an intermetallic Pt2Si MS (IM-Pt2Si-MS) electrode is demonstrated for the first time. Cyclic voltammetry (CV) curves reveal that the H underpotential deposition (H-UPD) peaks of the IM-Pt2Si-MS electrode shift to higher potentials than those of a Pt electrode, which indicates that hydrogen is more easily adsorbed on the Pt2Si surface. Thus, the IM-Pt2Si-MS electrode exhibited a higher HER activity than that of a Pt electrode in 0.5xa0M H2SO4 solution through linear sweep voltammetry (LSV). This is attributed to the electronic structure modification of Pt and the synergistic effect of the Pt–Si binary alloy in the IM-Pt2Si-MS electrode. In addition, the Tafel slope of 30.5 mV dec−1 indicates that the mechanism for the Pt2Si-catalyzed HER is Volmer–Tafel, for which the combined desorption of hydrogen is the rate-limiting step.

MoS 2 修饰ZnIn 2 S 4 微米球复合光催化剂的制备及光催化制氢活性增强研究

Abstract MoS2/ZnIn2S4 composites with MoS2 anchored on the surface of ZnIn2S4 microspheres were synthesized by a two-step hydrothermal process. The obtained samples were characterized by X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, ultraviolet–visible diffuse reflectance absorption spectroscopy, nitrogen adsorption–desorption measurements, photoluminescence spectroscopy, and photoelectrochemical tests. The influence of the loading of MoS2 on the photocatalytic H2 evolution activity was investigated using lactic acid as a sacrificial reagent. A H2 evolution rate of 343 μmol/h was achieved under visible light irradiation over the 1 wt% MoS2/ZnIn2S4 composite, corresponding to an apparent quantum efficiency of about 3.85% at 420 nm monochromatic light. The marked improvement of the photocatalytic H2 evolution activity compared with ZnIn2S4 can be ascribed to efficient transfer and separation of photogenerated charge carriers and facilitation of the photocatalytic H2 evolution reaction at the MoS2 active sites.

Preparation of electrolyzed oxidizing water with a platinum electrode prepared by magnetron sputtering technique

Electrolyzed oxidizing water (EO water) with low pH (2.2–2.7), high oxidation–reduction potential (ORP > 1100 mV), and available chlorine content (ACC) of 30–80 mg L−1 has an efficiently bactericidal activity and wide adaptability against many food-borne pathogens. EO water could be generated by electrolysis of a dilute NaCl solution in an electrolysis chamber with a Pt/Ti electrode. In this study, the Pt/Ti electrode was prepared by magnetron sputtering technique. The electrode surface has the characteristic of specific growth along the [111] direction. At the same time, the platinum electrodes prepared through thermal decomposition and electrodeposition as the control were also investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to study the performances of these three types of Pt/Ti electrode. The effects of the physicochemical properties of the Pt electrodes on their electrochemical behaviors were studied. Furthermore, the values of pH, ORP, ACC, Cl− and the sterilization effect of EO water using these Pt electrodes as anode materials have been systematically discussed. In addition, the content of HClO, ClO−, O3 and dissolved oxygen in EO water using the Pt-MS electrode has also been reported in this article.

Effect of electrode material and electrolysis process on the preparation of electrolyzed oxidizing water

Electrolyzed oxidizing water (EO water) bactericide is an indirect electrochemical sterilization technology, which is characterized by broad-spectrum, rapid and powerful sterilization. EO water, with a certain amount of available chlorine content (ACC), is generated by electrolysis of an extremely dilute NaCl solution. It is very important to study the preparation process of EO water, including electrode material and electrolytic process. In this paper, the effect of electrode material (platinum, iridium or ruthenium) on the physical and chemical parameters of EO water was investigated first. The effect of electrode composition and roasting temperature on the ACC of EO water was rigorously analyzed. The sterilization effect of EO water produced by different electrode materials was further discussed. In addition, the accelerated service lifetime of the electrode and exchange electrode polarity electrolysis were also investigated. Next, for the electrolysis process, the effects of ion exchange membrane type, current density and electrolyte concentration on the ACC of EO water, anode current efficiency and energy consumption were also studied. Finally, the stability of EO water, that is, the influence of illumination, heating and stirring on the physical and chemical parameters of EO water, was also observed in detail.

IrO2–TiO2 electrocatalysts for the hydrogen evolution reaction in acidic water electrolysis without activation

The development of highly active and long-term stable electrocatalysts for the hydrogen evolution reaction (HER) is very important. Because of the hysteresis phenomenon, IrO2 is rarely used as a cathode material for the HER. Herein, an IrO2–TiO2 composite oxide was prepared using the thermal decomposition method. The physical and electrochemical characterization of the materials was achieved by scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). In the process of the HER, the current of IrO2 is only 1.91 mA cm−2@−0.2 V in the first segment scan. However, at the 51, 101 and 151 segment scan, the HER current increases to 6.85, 15.7 and 18.2 mA cm−2@−0.2 V, respectively. During the activation process of IrO2, the HER current has increased ten times. Compared with the HER activity of IrO2, there is almost no hysteresis for the IrO2–TiO2 electrode. In the first segment scan, the HER current has already reached 27.9 mA cm−2@−0.2 V and further increased to 31.1, 33.1 and 35.0 mA cm−2 at the 51, 101 and 151 segment scan. The difference between them is not significant, which means that the IrO2–TiO2 electrode does not need activation. The IrO2–TiO2 electrode has exhibited a higher HER activity than the IrO2 electrode, which may be attributed to the electronic structure modification and the increase of the electrochemical area.

Facile Synthesis of Fluorine Doped Graphitic Carbon Nitride with Enhanced Visible Light Photocatalytic Activity

Fluorine doped graphitic carbon nitride (g-C3N4) was successfully synthesized by a convenient co-polycondensation of urea and ammonium fluoride (NH4F) mixtures, and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FTIR), UV-Vis diffuse reflectance absorption spectra (UV-DRS), nitrogen adsorption–desorption, photoelectrochemical measurement and photoluminescence (PL) spectra. The photocatalytic activities of fluorine doped g-C3N4 samples were evaluated by the degradation of Rhodamine B (RhB) solution under visible light irradiation. The results showed that the fluorine doped g-C3N4 had a better photocatalytic activity than that of undoped g-C3N4, which was attributed to the favorable textural, optical and electronic properties derived from the fluorine atoms substituting nitrogen atoms of g-C3N4 frameworks. The photoelectrochemical measurements confirmed that the charges separation efficiency was improved by fluorine doping g-C3N4. Moreover, the tests of radical scavengers demonstrated that the holes (h+) and superoxide radicals (⋅O2−) were the main active species for the degradation of RhB.

Biosorption of methylene blue from aqueous solution by natural Osmanthus fragrans powder

AbstractThe potential of Osmanthus fragrans powder as a natural biosorbent was investigated for the removal of methylene blue (MB) from aqueous solution. The effects of various experimental conditions including contact time, adsorbent dose, initial MB concentration, solution pH, salt ionic strength, and temperature on the adsorption properties of O. fragrans powder were discussed. The adsorption kinetic data were modeled using pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetics equations, indicating that the pseudo-second-order and intraparticle diffusion models could better describe the adsorption kinetics. Furthermore, adsorption equilibrium data were analyzed by Langmuir and Freundlich models, suggesting the Langmuir model presented a better correlation with the experimental data. The maximum adsorption capacities (qm) of O. fragrans powder for MB obtained from the Langmuir model were 155.52, 165.02, and 172.71xa0mgxa0g−1 at different temperatures of 288.15, 298.15, and 308.15xa0K, ...