Solid State Sciences最新文献

Using L-histidine as template, a three-dimensional (3D) open-framework cerium phosphite-oxalate, Ce₂(H₂O)₂(H₂PO₃)₂(C₂O₄)₃·C₆H₁₁N₃O₂·H₂O (1), has been synthesized under hydrothermal condition. Interestingly, it is the first example of lanthanide phosphite-oxalate with amino acid as the template. Compound 1 shows 3D framework with 8-, 12- and 20-ring channels and has a mog Moganite topology. A large amount of free water molecules and histidine cations are located in the channels of 1, which are favorable to the efficient proton transfer. Correspondingly, compound 1 displays temperature and humidity dependent proton conductivity with the highest value of 3.67 × 10⁻⁴ S cm⁻¹ at 75 °C and 98 % RH.

A magnetic α-Fe₂O₃/ZnNiFe₂O₄ composite photocatalyst was synthesized through a one-pot reaction employing choline chloride-ethylene glycol deep eutectic solvents and an incomplete sol-gel self-propagating method. The photocatalytic performance was assessed by removing methylene blue (MB) under 40 W visible light. With a 1.0 g/L catalyst dosage, 10 mg/L MB concentration, and pH levels of 6 and 12, removal rates of 97 % and 99 % were achieved within 90 min, respectively. The composite also demonstrated effective degradation of methyl orange (MO) and malachite green (MG). Stability tests revealed minimal reduction in photocatalytic activity after four cycles. Active species analysis identified ·O₂^⁻ and ·OH as the primary agents in the photocatalytic process. XRD, XPS, UV–VIS DRS, HRTEM, PL, and EIS analyses confirmed the formation of a Z-scheme heterojunction between ZnNiFe₂O₄ and α-Fe₂O₃, which enhanced the specific surface area, electron transport capacity, and narrowed the band gap. This heterojunction improved the separation efficiency of photogenerated electron-hole pairs, resulting in enhanced photocatalytic activity and stability. This study presents a novel approach for preparing Z-scheme heterojunction photocatalysts through a one-pot reaction.

NiFe₂O₄ has emerged as an efficient oxygen evolution reaction (OER) electrocatalyst, with outstanding stability in alkaline media and excellent redox properties. In order to further improve the catalytic performance, thinly-walled NiFe₂O₄ nanotubes (NiFe₂O₄-NTs), efficiently derivable from Ni, Fe, N-codoped carbon nanofibers, were innovatively synthesized through a sequential route combing hydrothermal, electrospinning, and high-temperature sintering in this work. The NiFe₂O₄-NTs possess large diameter of around 120 nm and their thickness of the tube wall is only about 10 nm. The surface properties of NiFe₂O₄ can be adjusted by forming the Ni-N/Fe-N bonds. Excitingly, largely exposed active surface area and boosted catalytic reaction kinetics toward oxygen evolution reaction are realized. The required overpotential to deliver 10 mA cm⁻² is only 331 mV, accompanied with favorable Tafel slope of only 51.8 mV dec⁻¹, small charge transfer resistance, and superior reaction stability.

In this study, the synthesized samples La_0.5Sm_0.2Sr_0.3Mn_1-xFe_xO₃ (x = 0.05, 0.15 and 0.20) were thoroughly investigated for their crystalline structure, electrical conductivity, and dielectric properties, the samples were prepared using autocombustion method. According to the X-ray diffraction study, the samples crystallized in an orthorhombic symmetry with the Pnma space group. To measure the dielectric characteristics, impedance spectroscopy was conducted over the temperature range of 100–260 K and a frequency range of 100 Hz to 1 MHz. Measurements of AC conductivity are indeed utilized to investigate the transport properties of materials being studied. The results indicated that both temperature and frequency significantly influence the conduction process. Three theoretical hypotheses were proposed to explain the hopping conduction: overlapping large polaron tunneling (OLPT), the non-overlapping small polaron tunneling (NSPT) mechanism, and correlated barrier hopping (CBH). It is also shown that the conductivity diminishes with an increase in Fe content. La_0.5Sm_0.2Sr_0.3Mn_1-xFe_xO₃ (x = 0.05, 0.15 and 0.20) can be used in electronic applications because of the high permittivity values confirmed by the dielectric measurements. With the aim of evaluating the distinct impacts of electrodes, grain boundaries, and grains on the complex impedance results, an appropriate alternative electrical circuit was utilized. Analysis of the sample's modulus indicated non-Debye characteristics and electrical relaxation phenomena. The materials exhibit good electrical properties, as well as strong chemical and thermal stability.

We present a high surface area sensor comprising NiO nanoparticles (NPs) incorporated within porous TiO₂ nanofibers (NFs), showing a remarkable response to acetone. Initially, we synthesized Polyvinylpyrrolidone (PVP) NFs containing titanium (Ti) and nickel (Ni) salts using a simple electrospinning method. Subsequent calcination of the PVP NFs led to the formation of NiO NPs embedded within the porous TiO₂ NFs. The resulting heterostructure material exhibited a significant response to acetone detection, with a ratio of electrical resistance in air (R_a) to that in the presence of gas (R_g) reaching 83 at its optimal operating temperature of 300 °C. Furthermore, it demonstrated stable performance under high relative humidity conditions.

The gas-phase and electrochemical hydrogenation properties of Nd_0.5Y_0.5MgNi_4-xCo_x (where x varies from 0 to 3) were studied. Samples were prepared using sintering and annealing procedures. X-ray diffraction analysis indicated that all the alloys were single-phase. The alloys readily absorbed hydrogen, and the crystal structures of the resulting saturated hydrides were refined. Nd_0.5Y_0.5MgNi₄H_4.2 and Nd_0.5Y_0.5MgNi₃CoH_4.4 belong to the NdMgNi₄H_3.6 structural type, while Nd_0.5Y_0.5MgNi₂Co₂H_5.5 and Nd_0.5Y_0.5MgNiCo₃H_6.0 belong to the LaMgNi₄H_4.85 structural type. Electrochemical studies revealed that the maximum discharge capacity of Nd_0.5Y_0.5MgNi_4-xCo_x electrodes increased from 236 mAh/g to 328 mAh/g as the cobalt content increased. The high-rate dischargeability (HRD₁₀₀₀) initially decreased from 48 % to 7 % with increasing cobalt content, but then increased to 32 % at the highest cobalt concentration. Additionally, the electrochemical kinetic properties were determined and compared for these electrodes, including the charge-transfer resistance (R_ct), polarization resistance (R_p), exchange current density (I₀), limiting current density (I_L), and hydrogen diffusion coefficient (D_H).

Photocatalytic water splitting for hydrogen production is an ideal strategy to relieve the energy crisis. In this work, Pt nanoclusters are employed as a co-catalyst to modify g-C₃N₄ for optimizing the photocatalytic hydrogen evolution performance. Compared with the pristine g-C₃N₄, the Pt nanoclusterss/g-C₃N₄ nanocomposites exhibit dramatic enhancement toward H₂ production, where the H₂ evolution rate of CN-Pt-C2 is nearly 425.1 times higher than pristine g-C₃N₄. The phase structure, morphology, optical properties, and surface chemical states of the fabricated samples are fully investigated. Based on the systematical characterizations, the reason for the enhanced H₂ generation performance is disclosed. It is expected this work can provide a valuable reference for the fabrication of a co-catalyst-based photocatalytic system.

Understanding how solids melt and determining their melting temperatures is of great significance for studying the properties of materials. Based on the main idea of Lindemann's melting criterion and the first-principles calculation of density functional theory, we proposed the atomic mean square displacement method to predict the melting temperature of the material. In this paper, the application range of this method for calculating melting temperature is extended. 8 kinds of Ⅱ-Ⅵ compounds were selected as verification objects. The results show the accuracy of our method in predicting the melting temperature of Ⅱ-Ⅵ compounds.