Zhandong Ren

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.

Purification of yellow phosphorus tail gas for the removal of PH3 on the spot with flower-shaped CuO/AC

The process of PH3 adsorption removal for purifying yellow phosphorus tail gas on the spot with flower-shaped CuO was investigated in this study. Flower-shaped and irregular-shaped CuO/AC adsorbents were prepared by hydrothermal and impregnation methods, respectively. They can effectively remove PH3 less than 1 mg m−3 and the purification efficiency is nearly 100% without fluctuation. However, the morphology of CuO on the adsorbent surface plays an important role in phosphine adsorption. The breakthrough adsorption capacity of the flower-shaped CuO adsorbent was 96.08 mg(PH3)/g(adsorbent), which was 2.23 times that for irregular-shaped CuO. The purification efficiency of the flower-shaped CuO was also influenced by temperature, oxygen volume fraction and space velocity. At a temperature of 100 °C and an oxygen volume fraction of 1.6%, the adsorption capacity is the best. The adsorbent can be renewed and the regenerated catalyst can also efficiently remove PH3 with a purification efficiency of nearly 100%. In the process of catalytic oxidation, according to XPS, we can conclude that CuO plays a very important role in phosphine adsorption and that oxygen is able to accelerate the oxidation of PH3 and oxidize Cu to regenerate the active species in the process of purification.

Synthesis and characterization of an IrO2–Fe2O3 electrocatalyst for the hydrogen evolution reaction in acidic water electrolysis

Water electrolysis is one of the most promising processes for a hydrogen-based economy, so the development of highly active, durable, and inexpensive catalysts for the hydrogen evolution reaction (HER) is very important. IrO2 is known to be one of the most active catalysts for the oxygen evolution reaction (OER) in a PEM electrolyzer, but the HER activity of IrO2 is rarely studied because of its low cathodic current compared to platinum. Herein, an IrO2–Fe2O3 composite oxide was prepared by a thermal decomposition method. The physical and electrochemical characterization of the material was achieved by scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Compared to that of IrO2, the CV curves of the IrO2–Fe2O3 electrode reveal that hydrogen is more easily adsorbed on the surface, which would lead to the H underpotential deposition (H-UPD) redox current increasing significantly. Therefore, the IrO2–Fe2O3 electrode exhibits higher HER activity than that of the IrO2 electrode in 0.5 M H2SO4 solution as shown by linear sweep voltammetry (LSV). It is attributed to the electronic structure modification of IrO2 and synergetic effect between Ir and Fe in the IrO2–Fe2O3 electrode. In addition, the Tafel slope of 36.2 mV dec−1 suggests that the mechanism for the IrO2–Fe2O3-catalyzed HER is Volmer–Heyrovsky.

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.