Search

Abstract: ZnGa2O4 phosphor doped with Eu3+ ions was synthesized by hydrothermal method using two concentrations: 3.34mol% and 1.67mol% of Eu3+. The crystal structure was investigated by means of X-ray diffraction, scanning electron microscopy and atomic force microscopy. The results indicate that the material consisting of ZnGa2O4:Eu3+ nanoparticles exhibits good crystalinity, with cubic spinel structure. The powders were found to have 4.74eV of ZnGa2O4:Eu3+ (3.34mol%) and 4.69eV of ZnGa2O4:Eu3+ (1.67mol%) band gaps, respectively. The luminescent analysis of the materials shows that the trivalent europium ions doped in this material are localized in different sites, substituting both Zn2+ and Ga3+. The emission spectra of the europium-doped samples, originating from 5D0–7F J (J =0–4) transitions, suggests the existence of three different site symmetry of Eu3+ ions, tetrahedral (Zn2+), distorted octahedral (Ga3+) and low octahedral (Ga3+) sites, respectively. [Copyright &y& Elsevier]

• Montmorillonite functionalized with LaMnO 3 were carried out for the first time. • By functionalization, physico-chemical properties of hybrid materials are improved. • HER and OER catalytic properties of electrodes modified have been studied. [Display omitted] Hybrid materials based on montmorillonite functionalized with LaMnO 3 perovskitic structures were obtained for the first time by ultrasonic method with sonotrode immersed in the reaction medium, followed by heat treatment at a temperature of 600 °C. The clay mineral montmorillonite (Mmt), sodium montmorillonite (Mmt-Na+) and functionalized material (Mmt-LMO) were characterized by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM/Edx) techniques. The XRD patterns of Mmt-LMO composites show both the presence of the perovskitic phase with orthorhombic structure, and a mixture of aluminosilicates, corresponding to the montmorillonite clay minerals. The (Mmt), (Mmt-Na+) minerals and (Mmt-LMO) hybrid material were used to manufacture modified electrodes whose catalytic properties for the oxygen and hydrogen evolution reactions were investigated in alkaline medium. Based on electrochemical experimental results, some of these electrodes are catalytically active toward the hydrogen evolution reaction and the more performant ones were investigated further and it was found that the electrode modified with the composition containing 6 mg LaMnO 3 functionalized montmorillonite and 10 µL Nafion solutions have the best electrocatalytic properties. At the current density of −10 mA/cm2 the electrode exhibits an over potentialfor hydrogen evolution of −0.48 V and its Tafel slope was measured to be 70 mV/dec. This study complements the extant scientific knowledge relevant to the water splitting domain. [ABSTRACT FROM AUTHOR]

Ni 11□ (HPO 3) 8 (OH) 6 nanorods were the focus of three different studies. First, the thermal behaviour of the material was investigated and it outlined a good thermal stability up to 400 °C. Second, a comparative electrochemical study concerning the OER performance in alkaline medium of several graphite electrodes modified with the nickel phosphite was performed. The most promising electrodes were further characterised electrochemically and the electrode modified with Nafion solution and 5 mg Ni 11□ (HPO 3) 8 (OH) 6 exhibited the smallest overpotential value at the 10 mA cm−2 anodic current density (0.59 V), as well as the smallest Tafel slope (0.081 V dec−1). Furthermore, the constant potential electrolysis test revealed that this electrode is fairly stable within a time span of 300 min. Third, the capacity of Ni 11□ (HPO 3) 8 (OH) 6 nanorods to remove MB and RhB were investigated under simulated visible light irradiation and positive results were obtained for the application as visible-light active photocatalyst. All this together corroborated with the eco-friendly nature of the materials, reinforces the fact that the phosphite type compound is a promising candidate for the design of new multifunctional and advanced materials. • Ni 11□ (HPO 3) 8 (OH) 6 acts as OER catalyst in alkaline medium. • Positive results were obtained for application as visible-light active photocatalyst. • Ni 11□ (HPO 3) 8 (OH) 6 has a good thermal stability in air up to 400 °C. [ABSTRACT FROM AUTHOR]

Nitrogen containing lanthanum manganite perovskite material has been successfully synthesized through sol-gel method using urea (CH 4 N 2 O) as a nitrogen source. The obtained powders were followed thermal treatment at low temperature. In order to achieve a comparative study on the obtained materials, three concentrations of urea were used (0.05; 0.1 and 0.15%). The characteristic of the materials were examined by differential thermal analysis (TG/DTA/HF), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), scanning/transmission electron microscope (SEM/TEM), energy-dispersive X-ray spectroscopy (EDX) and electrochemical measurements were made. The XRD patterns show that all analyzed sample are well crystallized and present a perovskite single phase with the cubic structure, space group: Pm-3m, with the average size of crystallites around 30 nm. All the N-doped LaMnO 3 perovskites exhibit remarkable electrocatalytic effect on the redox reaction of potassium ferricyanide improving redox peak current. Image 1 • Nitrogen doped LaMNO 3 materials was carried out for the first time. • Electrochemical behaviour of N–LaMnO 3 on graphite electrode was investigated. • By sol-gel technique was obtained nanometric particles with different morphologies. [ABSTRACT FROM AUTHOR]