Impact of the annealing temperature on perovskite strontium doped neodymium manganites nanocomposites and their photocatalytic performances (original) (raw)
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Scientific Reports, 2019
Nd1−xSrxMnO3 nanocomposites perovskites were synthesized using sol gel method at different Sr content x = 0.3, 0.5, 0.7, and 0.9. The photocatalytic performance of the Nd1−xSrxMnO3 nanocomposites for photodegradation of Acridine orange dye (AO) was evaluated over visible light illumination. The single phase of orthorhombic pbnm was formed for x = 0.3 and 0.5; however monoclinic and orthorhombic were observed at x = 0.7 and 0.9. The Energy gap of the Nd1−xSrxMnO3 nanocomposites were estimated for all concentrations to be in the range of 3 ± 0.05 eV. The photocatalytic efficiency of Nd0.3Sr0.7MnO3 nanocomposite was 95% of the initial AO dye concentration within 3 h illumination time. The linear increase of the photodegradation rate was found in our samples as a result of the increase of Sr contents from 0.3 to 0.7wt %. Interestingly, the Nd0.3Sr0.7MnO3 content has the highest degradation rate of AO which is two times faster than undoped NdMnO3. This superior behavior in photocatalytic...
Scientific Reports
In the present investigation, two sets of pure and substituted ferrite- and manganite-based mixed oxides were prepared within the stoichiometric formula$$A_{1 - x} A^{\prime}_{x} B_{1 - x} B^{\prime}_{x} O_{3}$$ A 1 - x A x ′ B 1 - x B x ′ O 3 , where A = Bi or La, A′ = Sr, B = Fe or Mn, B′ = Co, x = 0 or 0.2, by calcination at 700 °C (for 1 h) of corresponding metal citrate xerogels. Materials thus obtained were examined for bulk and surface characteristics using X-ray diffractometry, ex situ Fourier transform infrared spectroscopy, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and N2 sorptiometry. Their redox catalytic activity was evaluated towards a 2-propanol dehydrogenation reaction in the gas phase by employing in situ Fourier transform infrared spectroscopy. The results obtained could help reveal that (1) the presence of Bi (versus La) and Mn (versus Fe) facilitated the formation of polymeric crystalline phases assuming lattice-charge imbalance (...
European Journal of Inorganic Chemistry, 2007
Keywords: Mixed-valent compounds / Perovskite phases / Magnetic properties / X-ray absorption near-edge spectroscopy (XANES) / Topotactic reaction Thermogravimetry, X-ray and electron diffraction and high resolution electron microscopy show that the reduction process from perovskite La 0.5 Ca 0.5 MnO 3 to brownmillerite La 0.5 Ca 0.5 MnO 2.5 is a reversible topotactic process. Two series of monophasic La 0.5 Ca 0.5 MnO 3-δ oxygen-deficient perovskites were stabilized in the 0 Յ δ Յ 0.12 range, either from reduction of La 0.5 Ca 0.5 MnO 3 or oxidation of La 0.5 -Ca 0.5 MnO 2.5 . Soft X-ray absorption spectroscopy shows that Mn oxidation states differ as a function of the synthetic path-
Chemical engineering transactions, 2020
Perovskite-type rare earth orthoferrite (ReFeO3) nanocrystalline were synthesized by using sol-gel citrate method and followed by calcination from oxalate salt Re2(C2O4)3, which composed of Nd (76.5 %), Pr (14.8 %), Dy (5.5 %) and Tb (3.2 %) recovered from discarded neodymium magnets (NdFeB) in hard-disk-drive waste. The synthesized materials were characterized by X-ray diffraction (XRD), field emission scanning electron microscopes (SEM), Brunauer-Emmett-Teller nitrogen adsorption and desorption (BET), Ultraviolet-visible diffuse reflection spectroscopy (UV-Vis DRS). The perovskite NdFeO3 was synthesized under the same conditions from an analytical grade pure salt to be used as a control material. Photocatalytic characteristics of both perovskite ReFeO3 and NdFeO3 were investigated through evaluation of methylene blue (MB) degradation under visible light. The degradation efficiency of MB by the ReFeO3 catalyst was higher than that by NdFeO3 after 3 h of illumination under visible l...
Nanocomposite Structure and Reactivity of Perovskites Based on Lanthanum Manganites
Russian Journal of Physical Chemistry a, 2012
Data on the real/defect structure of anion excess lanthanum manganites are analyzed. It is shown that low temperature materials, especially those synthesized with the use of organic additives, form nano composite structure due to stabilization of manganese and dopant cations in highly charged states (≥4+) at anion excess. It is established that domains (layers) with perovskite structure containing point defects are sep arated/intergrown by extended defect regions enriched with lanthanum or promoter cations. It is noted that the composition and concentration of extended defects are controlled by the conditions of synthesis, the cal cination temperature, and the nature of the promoter; these defects, which are partly retained after high tem perature treatment, can affect the functional properties of materials. Features of the cation and anion modi fication of lanthanum manganites and the reactivity of nanocomposite structures with respect to oxidation reactions are analyzed. It is concluded that at a high content of weakly bound oxygen and a noticeable mobil ity of the lattice oxygen, the activity of these materials in various oxidation reactions is determined by their defect structure and specificity of the catalytic action.
Photocatalytic Properties of Ordered Double Perovskite Oxides
2011
Ordered double perovskite oxides (A 2 BB'O 6 , AA'BB'O 6) which contained W, Ta, Nb and Ti were synthesized, and the applicability of the oxides to photocatalytic reaction was discussed. The stability of the oxides strongly depended on the constituent atoms, especially B-site cations. Ta-, Nb-and Ti-containing perovskites were stable under two types of photocatalytic reaction conditions, namely, H 2 evolution from aqueous methanol solution and O 2 evolution in Ag + ion-containing aqueous solution. Among the perovskite oxides, La 2 ZnTiO 6 showed catalytic activity for the latter reaction and the rate for O 2 evolution normalized by catalyst surface area was one third of that of TiO 2 .
Revisiting the Role of Vacancies in Manganese Related Perovskites
The Open Inorganic Chemistry Journal, 2007
Oxygen engineering is an important tool for on-demand tailoring of manganese related perovskites into optimized performances. Anionic vacancies can be induced in both doped and undoped manganites by means of topotactic reduction processes under oxygen controlled atmosphere. This has given rise to the stabilization of new phases as a consequence of ordering of oxygen vacancies in which Mn 2+ appears due to the reducing process. Different reduction pathways are proposed for LaMnO 3 and doped systems. FM interactions remain at the octahedral layers when vacancies are longrange ordered. The peculiar magnetic behaviour of new layered perovskite superstructures is discussed.
Journal of Environmental Chemical Engineering, 2024
Perovskites, a group of materials with various optical, chemical, and physical properties, when coupled with different nanostructures, can become the most versatile and multipurpose with vast potential. Perovskites have shown great promise in photocatalysis, where light energy harvesting supports various applications. The properties of perovskites can be controlled by manipulating their crystal structure, size, morphology, and chemical composition. This review focuses on numerous perovskites and perovskite-based heterostructures, and their photocatalytic applications. Additionally, diverse synthesis methodologies used to obtain perovskite-based heterostructures have been highlighted. The structure and types of perovskites are thoroughly addressed along with the discussions of the various applications of perovskite-based heterostructures in the fields of energy and environment. This includes H 2 generation, CO 2 conversion, N 2 fixation, photovoltaics, organic synthesis, pollutant degradation, disinfection, and the development of self-cleaning surfaces. The future prospects have been presented to get insights into the potentials of perovskites and perovskite-based heterostructures as photocatalysts for various applications.
Electronic Structure of Tantalum Oxynitride Perovskite Photocatalysts
Chemistry of Materials, 2013
The tantalum oxynitride perovskites ATaO 2 N (A = Ca, Sr, and Ba) and PrTaON 2 are promising candidates for the photocatalytic splitting of water under illumination with visible light. A combination of X-ray photoemission spectroscopy (XPS), Kelvin probe force microscopy (KPFM), UV−vis spectroscopy, and depth-resolved cathodoluminescence spectroscopy (DRCLS) has been used to determine the absolute conduction and valence band energy levels of these four compounds. All have conduction band edges that lie above the reduction potential for water and therefore are suitable for the photocatalytic production of hydrogen, whereas the valence band edges lie near the oxidation potential of water. The position of the conduction band edge is closely linked to the Ta−O/N−Ta bond angles and hence tilting of the octahedra, whereas the position of the valence band edge is more sensitive to the oxygen-to-nitrogen ratio.
Visible-Light-Enhanced Photocatalytic Activity of Totally Inorganic Halide-Based Perovskite
ChemistrySelect, 2018
The removal of contaminants is an interesting topic in environmental research and for society nowadays. In this sense, perovskite materials have proven to be amazing photocatalysts. In this study, CsSnBr 3 perovskite was synthesized and characterized using techniques such as x-ray diffraction, Raman spectroscopy, x-ray photoelectron spectroscopy and UV-vis spectroscopy. A mixture of cubic and tetragonal crystalline phases was found in the sample, and XPS revealed the presence of two oxidation states for Sn, and the formation of surface non-stoichiometric tin oxide. A good light harvesting in the visible range of the electromagnetic spectrum was also found for the perovskite synthesized, which is also insoluble in water. Furthermore, adsorption and photocatalytic tests were performed. Degradation of crystal violet dye was found after the adsorption tests, but the adsorption rate affected the photocatalytic process. Therefore, CsSnBr 3 shows a good photocatalytic activity for degrading dyes and contaminants.