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Particularities of trichloroethylene photocatalytic degradation over crystalline RbLaTa2O7 nanowire bundles grown by solid-state synthesis route
摘要： This is the first report on synthesis and photocatalytic activity for trichloroethylene (TCE) degradation under simulated solar light over RbLaTa2O7 layered perovskites with predominant nanowire or platelet morphologies. SEM images witnessed that the one step thermal treatment at 1200 °C lead to formation of RbLaTa2O7 nanowires with diameter of 80~320 nm and several microns in length associated in bundles and sharp-edged, merged platelets (minor phase). The two-step annealing at 950 °C and 1200 °C resulted in decrease of wires bundle population and increase in that of platelets merged in facetted particles. The RbLaTa2O7 nanowires are made of by well-aligned atomic rows with preferred orientation toward the c-axis, relatively free of defect. High density of hydroxyl groups on the sample calcined in mild conditions (RbLaTa_01) favors the photo mineralization of TCE. In contrast, the activity of RbLaTa_02 annealed in harsh conditions (950 and 1200 oC), poor in surface hydroxyl groups, remained modest. The weak surface basicity directed the reaction mainly to generation of intermediate chlorinated compounds. Pd and Au were supported on RbLaTa2O7 perovskites as an alternative strategy to boost the removal of chlorinated pollutants by combining photocatalytic (mineralization) and catalytic (hydrodechlorination, HDC) processes. The mineralization of TCE to Cl- was drastically hindered in presence of methanol due to quenching of ?OH radicals by alcohol. The results suggested that the density of RbLaTa2O7 surface hydroxyl groups is essential for photo mineralization of TCE whereas the surface carbonate is beneficial for the formation of intermediate chlorinated product.
关键词： solid state reaction,layered perovskites,trichloroethylene,simulated solar light,photocatalysis
更新于2025-09-23 15:21:21
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Cation Exchange as a Mechanism to Engineer Polarity in Layered Perovskites.
摘要： Cation exchange reactions performed on the n = 2 Dion-Jacobson phases RbNdNb2O7 and RbNdTa2O7, using LiNO3 and NaNO3, yield the corresponding LiNdM2O7 and NaNdM2O7 (M = Nb, Ta) phases. Synchrotron X-ray and neutron powder diffraction data, in combination with second-harmonic generation data and supported by first-principles DFT calculations, reveal that the LiNdM2O7 phases adopt n = 2 Ruddlesden-Popper type structures with an aˉaˉc+/-(aˉaˉc+) distortion described in the polar space group B2cm. In contrast, the NaNdM2O7 phases adopt n = 2 Ruddlesden-Popper type structures with an aˉb0c0/b0aˉc0 distortion, described in the centrosymmetric space group P42/mnm. The differing structures adopted by the LiNdM2O7 and NaNdM2O7 phases are rationalized on the basis of a competition between i) optimizing the size of the Li/Na coordination site via octahedral tilting and ii) ordering the Na/Li cations within the (Li/Na)O2 sheets to minimize cation-cation repulsion – the former appears to be the dominant factor for the Li phases and the latter factor dominates for the Na phases. The strong A’-cation dependence of the tilting distortions adopted by the A’NdM2O7 phases suggests that by careful selection of the substituting cation the tilting distortions of layered perovskite phases can be rationally tuned to adopt polar configurations, and thus new ferroelectric phases can be synthesized.
关键词： Layered perovskites,Cation exchange,Structural distortion,Ferroelectric materials,Polarity engineering
更新于2025-09-23 15:21:01
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Toward Phase Stability: Dion–Jacobson Layered Perovskite for Solar Cells
摘要： Three-dimensional halide based perovskites has emerged as promising semiconducting light harvester for thin-film solar cells fabrication, however, its intrinsic instability under humidity restricts their potential commercialization. To address such challenges, the development of low-dimensional Dion-Jacobson (DJ) phase / layered perovskites have recently gained substantial attention due to their intriguing environmental stability and competitive power conversion efficiency. In this review, we have screened and focused our investigation on the DJ phase in layered perovskite for solar cell fabrication, especially elucidation on the active role played by organic spacer cation for active layer. We also discuss the possible strategies that can be employed to further push the performance of DJ perovskite solar cells.
关键词： organic spacer cation,layered perovskites,Dion-Jacobson phase,phase stability,solar cells
更新于2025-09-11 14:15:04
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Synthesis, Optical and Magnetic Properties of Six-Layered Aurivillius Bismuth Ferrititanate
摘要： This work reports the preparation, structure, photochemical and magnetic properties of six-layered Aurivillius bismuth ferrititanates, i.e., Bi7Ti3Fe3O21, Bi7(Ti2Nb)Fe3O21+δ and Bi7(Ti2Mg)Fe3O21-δ nanoparticles. The samples were prepared through the modified citrate-complexation and precursor film process. XRD Rietveld refinements were conducted to study the phase formations and crystal structure. The morphological and chemical component characteristics were investigated via some measurements such as SEM, TEM, and EDX analyses. Bi7Ti3Fe3O21, Bi7(Ti2Nb)Fe3O21+δ and Bi7(Ti2Mg)Fe3O21-δ nanoparticles present an indirect allowed transitions with band energy of 2.04, 2.03, and 2.02 eV, respectively. The hybridized (O2p+Fet2g+Bi6s) build up the valence band (VB), and electronic components of (Ti-3d+Fe-eg) form the conduction band (CB) of this six-layered Aurivillius bismuth ferrititanate. Three samples have obvious abilities on the photocatalytic degradation on Rhodamine B (RhB) dyes via the excitation wavelength λ> 420 nm. The optical absorption, photodegradation and magnetic abilities were improved through micro-structural modification on “B” site via partial substitution of Mg2+- and Nb5+- for Ti4+. The photocatalytic results were discussed on the layer structure and multivalent Fe ions. Fe3+/2+ in the perovskite slabs (Bi5Fe3Ti3O19)2? could act as the catalytic mediators in the photocatalysis process. As a photocatalyst, Aurivillius Bi7(Ti2Mg)Fe3O21-δ nanoparticle is advantageous due to its photocatalytic and magnetically recoverable abilities.
关键词： Nanoparticles,Layered perovskites,Band structure,Semiconductors,Photocatalysis,Aurivillius phases
更新于2025-09-10 09:29:36