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In this work, Tungsten(W)-doped TiO 2 nanoparticles were synthesized using the sol–gel method and were used as electrode materials in supercapacitor applications. The structural and morphological properties of the prepared samples were analyzed by means of XRD, STEM, TEM, and XPS. The analysis of the defect centers was carried out using EPR spectroscopy. The electrochemical analysis of the assembled supercapacitor was done using cyclic voltammetry, galvanostatic cycling with potential limitation technique, potentiostatic electrochemical impedance spectroscopy, and voltage-holding experiments. All the presented samples showed paramagnetic defects in the EPR analysis, while 0.5% W-doped TiO 2 showed a maximum signal intensity. The supercapacitor performance from the synthesized electrode material showed highly encouraging results. The equivalent series resistance (R s ) value for all the designs showed values under "1 Ω ," which reflects high conductivity. As the maximum EPR intensity comes from TiO 2 doped with 0.5% W, the supercapacitor performance of this sample was tested with a newly designed five-electrode system. This design showed superior performance compared to any other used designs with a specific capacitance of 25.5 F g - 1 , with an energy density of 14.16 Wh kg - 1 at 302 kW kg - 1 . [ABSTRACT FROM AUTHOR]

In this work, PVDF membranes coated with ZnO particles were prepared to study the influence of the loading concentration on RhB pollutant removal. The PVDF membranes prepared by phase inversion method contain a mixture of α and β phases as identified by correlating the XRD and FT-IR results. The mean pore size evaluated by SEM measurements is about 4 μm and the asymmetric structure of the membrane was highlighted. The presence of ZnO particles on PVDF membrane was evidenced by XRD, SEM and EXD measurements. By coating with ZnO particles the hydrophilic character of the membrane was improved. The RhB removal was realized using a combined process of two competitive methods: adsorption and photocatalysis. By increasing the ZnO loading the removal efficiency was enhanced. Additionally, the electron spin resonance spectroscopy coupled with spin trapping technique was used to evidence the generation of reactive oxygen species during irradiation, the presence of both hydroxyl radical and superoxide radical being proven. [ABSTRACT FROM AUTHOR]

SnO2–TiO2 nanocomposites are prepared by growing TiO2 nanoparticles onto the preformed SnO2 nanoparticles. The SnO2 core nanoparticles ware obtained in the presence of two different surfactants, namely hexadecyltrimethyl ammonium bromide and polyethylene glycol 600 (PEG600), by chemical precipitation followed by a thermal treatment at 500 °C. The TiO2 was obtained directly on modified SnO2 nanoparticles by a sol–gel process. A sample without surfactants was prepared in the same conditions. The processes involved during annealing of precursors were revealed by TGA-FTIR. The crystalline and mesoporous structures of samples were evidenced by XRD, HRTEM and by N2 adsorption–desorption isotherms. XPS investigations highlighted the interface modifications due to the presence of cationic or anionic moieties resulted from the thermal decomposition of surfactants. Combined UPS and UV–Vis measurements allowed the determination of the oxidation energies, band gaps and energy bands alignment of nanocomposites. The photocatalytic activity based on reactive oxygen species (ROS) generation was studied toward degradation of RhB under visible-light irradiation and by the use of EPR coupled with spin-trapping technique. It was found that the generated ROS are only of ·OH type and, this specific process, is analyzed in terms of energy bands alignment. [ABSTRACT FROM AUTHOR]

Fe3O4-SnO2 nanocomposites with SnO2 in the reduced form (without post-annealing) were prepared. X-ray diffraction, high resolution TEM microscopy, X-Ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy and magnetization measurements were used for sample characterizations. Additionally, nitrogen adsorption-desorption isotherms and surface area measurements (BET) were made for porosity and surface area determination. Depending on the amount of SnCl2 used in preparation, tetragonal tin oxide hydroxide Sn6O4(OH)4 or SnO secondary phases were also formed in various samples. XPS analysis shows the presence of surface Sn2+ states and as well as lack, or non-detectable, interstitial tin inside SnO2 nanocrystallites. The presence of Sn2+ surface states determines important changes of both magnetic and photocatalytic properties of samples. Thus Sn2+ surface states determine, on the one hand, an increased efficiency of photocatalytic processes and, on the other hand, a significant decrease of the saturation magnetization of Fe3O4 cores. Moreover, by using ESR spin trapping technique, the generation of reactive oxygen species (·OH, O2·−) resulted by light irradiation of samples was evidenced. [ABSTRACT FROM AUTHOR]