Solid State Sciences最新文献

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.

As a novel cathode material for sodium-ion batteries, Na₃MnTi(PO₄)₃ (denoted as NMTP) has received great attention because of its abundant natural resources, excellent safety, low toxicity as well as three-electron reactions. Unfortunately, the pure NMTP cathode displays a bad conductivity, resulting in an inferior electrochemical performance for sodium energy storage. Herein, we introduce a good route to fabricate the nitrogen-doped graphene-decorated NMTP@C (denoted as NG-NMTP@C) composite with superior rate property and superior cycle stability for the first time. In this fabricated material, the nitrogen-doped graphene nanosheets are dispersed into the NMTP@C particles. Compared to NMTP@C, the prepared NG-NMTP@C cathode possesses better cycle stability and higher capacity. It shows the capacity of 173.1 mAh g⁻¹ at 0.1 C and presents the high capacity retention of around 97.1 % at 10.0 C over 400 cycles. Therefore, this fabricated NG-NMTP@C nanocomposite can be employed as the novel positive electrode in sodium-ion storage.

In depth understanding of the magnetic, structural and electrical properties of Heusler alloys are crucial to achieve potential applications in spin-based device. Wherein, we report the synthesis of Cr₂MnAl Heusler alloy nanoparticles (NPs) via co-precipitation method and also demonstrated their transport properties. Interestingly X-ray analysis confirms the cubic phase of the synthesized Heusler alloy NPs and transmission electron microscopy (TEM) analysis reveals that the Cr₂MnAl as particle size of 10 ± 2 nm. Moreover, this particle size has adverse effect on symmetry of Cr₂MnAl Heusler alloy due to their higher surface to volume ratio that significantly changes their magnetic and electrical properties. These NPs exhibit soft ferromagnetic properties with a Curie temperature (Tc) of 25 K. Besides, resistivity measurements indicate the semiconducting nature and also we report the observation of anomalous Hall effect. In addition, we support our experimental results by studying the electronic and magnetic properties of alloy using first principle calculations. This density functional theory reveals that Cr₂MnAl has half metallic characteristics with high spin polarization. In light of above, this material can be used as intermediate layer to decouple the two ferromagnetic layers which acts as spin-polarized carriers in spin-based device.

A new Mg-containing disordered quaternary telluride Mg_1.2(1)In_1.2(1)Si₂Te₆ is prepared at 1223 K by direct fusion of elements. This mixed metal telluride adopts a trigonal (P$\bar{3}$1m space group) structure having refined cell constants of a = b = 7.0603(3) Å and c = 7.1681(4) Å. Four unique crystallographic sites are filled in the structure: one disordered metal site (In1/Mg1), one partially filled Mg2, one Si1, and one Te1. Each metal ion (In and Mg) in the structure sits at the center of a distorted octahedron of Te1 atoms. Two Si atoms are involved in forming an ethane-like Si₂Te₆ unit with the help of a Si−Si bond. The local coordination environment around each Si atom can be described as a distorted tetrahedron comprising one Si1 and three Te1 atoms. A polycrystalline sample with the loaded composition of Mg_1.2In_1.2Si₂Te₆ shows an optical bandgap of 1.02(2) eV. The p-type semiconducting nature of the Mg_1.2In_1.2Si₂Te₆ sample was established from the positive values of the Seebeck coefficient (S) and resistivity studies. The complex structure of the Mg_1.2In_1.2Si₂Te₆ phase, which features heavy elements (In and Te), helps to achieve ultralow total thermal conductivity (k_tot) of 0.33 W/mK at 773 K.

The Ni-doped CoFe₂O₄ graphene composites (Ni-CFO/RGO) have been successfully prepared using the microwave-assisted method. The substance is a novel nanocomposite structure in which CoFe₂O₄ nanoparticles are tightly and uniformly attached to graphene hybrid nanosheets. The synergistic effect of Ni doping and CoFe₂O₄ can reduce the volume expansion of CoFe₂O₄ in the reaction process and inhibit the stacking of graphene. Because the Ni-CFO/RGO composite is structurally stable during the electrochemical reaction, it has a good theoretical capacity. Excellent carbon composite can further enhance the electron transport performance and structural stability of the material, thereby improving the electrochemical performance and cycle life of the material. Doping Ni²⁺ into metal oxides can not only form oxygen vacancies, and improve the transport capacity of sodium ions, but also broaden the electron transport channel. In addition, the catalyst can form a composite structure with metal oxide, which can effectively inhibit its volume expansion. At the same time, reacting with carbon materials, can also effectively reduce the accumulation of carbon, thereby reducing its resistance. After 200 cycles at a current density of 0.05 A g⁻¹, it can provide a high sodium storage capacity of 380.6 mAh g⁻¹, which still keeps 203.4 mAh g⁻¹ at 1.5 A g⁻¹.

In layered perovskites with the Carpy-Galy structural type, similar structural phase transitions occur under high pressure. These structural changes, which are crucial for the pressure-induced phase transition in layered perovskite, were analyzed based on experimental X-ray diffraction data. The tilting of the Ti-O₆ octahedra and the distortion of the arrangement of rare-earth atoms were studied in detail. Changes in these structural features in layered perovskite serve as common indicators of the phase transition to the monoclinic phase that occurs under high pressure application.

The conversion of CO₂ into fuel using photocatalytic technology is critical in reducing greenhouse gas emissions and addressing the energy issue. In this paper, type II heterojunctions of 2D/2D BiOIO₃/Bi-MOF were built using the solvothermal approach. The materials were characterized utilizing methods such as XRD, SEM, TEM, XPS, UV–vis diffuse reflection, and an electrochemical workstation. Under 300 W Xenon lamp irradiation, BiOIO₃/Bi-MOF-30 (BOIOB-30) produced 21.26 μmol/g/h of CO, 1.95 times greater than pure BiOIO₃. This improvement is related to the alteration of BiOIO₃ with lamellar Bi-MOF, which provides more reactive sites and significantly increases the composite's photocatalytic activity.