Materials Research Bulletin最新文献

In this work, niobium diboride (NbB₂) nanoparticles were successfully synthesized using a simple and facile molten salt method and examined as electrodes for supercapacitors. The synthesized nanoparticles were characterized using SEM, HRTEM, XRD, XPS, and BET techniques. Also, the electrochemical performance of various NbB₂ nanoparticles depending on the various amorphous boron concentrations was systematically investigated using both a neutral (1 M Na₂SO₄) and a basic (6 M KOH) electrolyte. Electrochemical analysis revealed that the obtained sample denoted as the NbB₂–8 exhibited the best electrochemical performance (159.6 F/g at 10 mV/s) in Na₂SO₄ electrolyte compared to that of the KOH electrolyte (69.6 F/g at 10 mV/s). Such a result can be owing to the size and mobility of ions in the electrolyte. Overall, this work could pave the way for other metal borides’ versatility and potential in energy storage.

Lithium-rich layered oxides (LLO) possessing high specific capacity has the limitation of voltage fade, poor high C-rate performance and low conductivity. Spinel coating on LLO surface is known to mitigate the voltage fade, however, enabling high C-rate performance remains challenging. In this study, LLO nanofiber core with composition 0.6Li₂MnO₃·0.4LiMn_0.25Ni_0.38Co_0.37O₂ is prepared by electrospinning process and the same is coated with spinel LiMn_1.5Ni_0.5O₄ shell to obtain LLO/spinel (LLO/S) core-shell heterostructure. The spinel shell coating is accomplished (i) by a novel co-axial (CA) electrospinning process and (ii) by wet chemical (WC) approach. The CA electrospinning process provides a uniform core-shell structure compared to the WC process. The electron microscopy studies reveal the fibrous microstructure in LLO/S heterostructures with energy dispersive spectroscopy compositional mapping showing the spinel composition on the surface. Higher concentration (>10 wt.%) of spinel coating are shown to break the fibers into particulates. X-ray diffraction and high-resolution transmission electron microscopy analysis confirm the spinel structure formation along with layered structure. While the capacity is slightly compromised compared to the pristine LLO nanofiber, the LLO/S heterostructure with 10 wt.% spinel coating exhibits a high reversible capacity of 268 mAhg^-1 with minimal capacity loss during the 1st cycle (with coulombic efficiency 83.5%) and an excellent high C-rate capability (88 mAhg^-1 at 10C-rate and 55 mAhg^-1 at 20C-rate). The electrochemical studies also demonstrate the importance of optimal spinel content in the coating and the method of spinel coating on the layered material surface. The encapsulation of LLO with spinel layer which has 3D-diffusion pathways for Li-ion transport facilitates high ionic and electronic conductivity and hence leads to enhanced electrochemical performance of LLO/S heterostructured cathodes.

Polymers and fillers with high dielectric constant (ε_r), charge-discharge efficiency (η) and breakdown strength (E_b) are fundamental to the development of nanocomposite dielectrics for superior energy storage capabilities. Herein, high-ε_r P(VDF-TrFE) is used to prepare the P(VDF-TrFE)-g-PMMA matrix with elevated ε_r and η, then the P(VDF-TrFE)-g-PMMA/BNNS-NH₂ nanocomposites with uniformly oriented distribution of h-BN is obtained by a squeegee casting process using amino-boron nitride (BNNS-NH₂) as fillers. Thanks to the limiting effect of PMMA and the high insulating effect of BNNS-NH₂, the energy storage density (U_e) of the nanocomposite is up to 15.1 J/cm³ at 500 MV/m, which is 358 % and 182 % of the original P(VDF-TrFE). Furthermore, the η could reach to 72 %, being 184 % of neat polymer. These results demonstrate that the coordinated enhancement of U_e and η is critical for high performance energy storage, which provide scientific and technological support for the practicability of PVDF-based dielectrics.

With the increasing application of electronic materials in various fields such as flexible electronic textiles, wearable and portable gadgets, aerospace and aircraft systems etc., the demand for clean high-power energy storage devices is also increasing rapidly. To date, the application of market available supercapacitors has not met the energy expectations in the range of market leading Li-ion batteries (LIBs) due to their unreliable mechanical flexibility, electrolyte leakage, low voltage application, low capacity, low cycle stability and moderate rate-capability. Inappropriate utilization of the maximum porosity of the electrode material and inefficient activities of the electrode/electrolyte interface are major challenges for present supercapacitor development. In this work, for the first time, the role of polymer gel electrolyte infiltration to improve the electrochemical performance of a supercapacitor has been explicitly studied and investigated. It has been observed that 1-Ethyl-3- Methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][TFSI] ionic liquid electrolyte embedded in Polypropylene Carbonate (PPC) and Polycarbonate (PC) polymer matrix polymer gel electrolyte (PGE) showed excellent supercapacitive performance at high voltage window 2.6 V by delivering maximum total capacitance of 5.81 F and maximum energy density 10.9 Wh kg^-1 at 30 mA current (0.06 A g^-1). Regular infiltration of the polymer gel electrolyte inside the electrode material is also observed during long cycle operation of 10,000 cycles. Infiltration of electrolyte ions into the pores of electrode materials plays a significant role in increasing capacitance and cycle Stability. These results highlight the potential of this novel high-voltage polymer gel electrolyte for future high-power energy storage device applications.

The great potential for electromagnetic wave (EMW) absorption is revealed in two-dimensional (2D) Ti₃C₂T_x (MXene) thin sheets that have numerous surface flaws and an extensive spectrum of functional groups. In this study, Ti₃AlC₂ (MAX Phase) is etched, and then ultrasonic exfoliation is used to create 2D ultrathin Ti₃C₂T_x nanosheets; a type of MXene. The MnCo₂O₄ spherical particles were grown on the layered structure of Ti₃C₂T_x via a one-pot hydrothermal process. The synthesized Ti₃C₂T_x/MnCo₂O₄ composite provides superior bulk-to-surface and interfacial charge transfer capabilities due to their short charge transfer distance and extensive interface contact area to the EMW. This article thoroughly evaluates the loss impact in Ti₃C₂T_x/MnCo₂O₄ absorbers as -44.4 dB of reflection loss at 16.04 GHz with a thickness of 5.114 mm for the first time, which is essential for fabricating an effective microwave absorber.

This work explores the mechanical, electronic, dynamical stability, optical, and thermoelectric properties of Nb-based copper sulvanite compounds Cu₃NbX₄ (X=S, Se, Te) at 0, 5, 10, 15, and 20 GPa isotropic pressure within the framework of density functional theory (DFT). Calculated results are found in good agreement with experimental data, specifically in the values of their lattice parameters and optical band gaps. Cu₃NbX₄ exhibits promising optical properties for photovoltaic applications with enhanced properties under pressure. Exploration on transport properties also shows moderate thermoelectric figure of merit with slight improvement under pressure.

Novel Ba₂RE₂Si₄O₁₃ (RE = La, Nd, Sm, Eu, Gd, Ho, Er and Yb) ceramics were prepared by traditional solid reaction methods. The phase compositions of Ba₂RE₂Si₄O₁₃ ceramics were explored. The triclinic structure with P$\overline{1}$ space group of Ba₂RE₂Si₄O₁₃ ceramics was confirmed by TEM and Rietveld refinement analyses, and the decrease in the ionic radius of RE³⁺ induced the phase transition from low symmetry (triclinic) to high symmetry (monoclinic) between Ba₂Sm₂Si₄O₁₃ and Ba₂Eu₂Si₄O₁₃. ε_r-exp of the Ba₂RE₂Si₄O₁₃ ceramics was significantly affected by ionic polarisability. The ‘rattling and compressing effects’ of cations also affected the ε_r-exp of Ba₂RE₂Si₄O₁₃ ceramics. The intrinsic dielectric loss of Ba₂RE₂Si₄O₁₃ ceramics were evaluated by the far-IR reflectivity spectrum, and high Q × f values of the Ba₂Nd₂Si₄O₁₃ and Ba₂Eu₂Si₄O₁₃ ceramics were attributed to their large total lattice energy and activation energy. The average bond valence of RE³⁺ played an important role in controlling the τ_f values of the Ba₂RE₂Si₄O₁₃ single-phase ceramics, and the high average bond valence of RE³⁺ corresponded with the small negative τ_f values. Great microwave dielectric properties (ε_r = 11.52, Q × f = 33,600 GHz at 11.80 GHz and τ_f = ‒25.6 ppm/ °C) were obtained in the Ba₂Nd₂Si₄O₁₃ single-phase ceramic.

Poly(3,4-ethylenedioxythiophene) (PEDOT) films were electrochemically synthesised with sodium dodecylbenzenesulfonate (DBS) and chloride acting as dopant anions within the polymer matrix. Upon redox switching of the PEDOT/DBS film between conducting and non-conducting states, the DBS anion remained within the polymer and cation insertion and expulsion occurred, as confirmed by Electrochemical Quartz Crystal Microbalance (EQCM) measurements. Electrolytes composed of alkali metal cations of varying masses (Li⁺, Na⁺, K⁺) were employed to investigate the cation insertion/expulsion processes, thereby resulting in varying mass changes being observed upon film redox switching. The charging and discharging of bulky anion doped polymer films presented higher capacitance upon charging and lower capacitance when discharging, which is expected during doping and de-doping as confirmed by AC impedance. In this work, the main results obtained by chemical-physical characterisation are presented and critically discussed, with regard to the possible use of a viable conducting polymer as a drug delivery vehicle.

In the present work, alumina-supported trimetallic Pd-Rh-Ru catalysts were synthesized and studied in comparison with the bimetallic Pd-Rh reference sample. The alloy nanoparticles were formed on the surface of the alumina support by thermolysis of the complex salts [Rh(NH₃)₅Cl][Pd(NO₂)₄] and [Rh(NH₃)₅Cl]_0.5[Ru(NH₃)₅Cl]_0.5[Pd(NO₂)₄], preliminary deposited via an incipient wet impregnation method. The influence of the conditions of the thermolysis process on the phase composition of the final products and the size of the trimetallic particles was established. Thus, nanoscale trimetallic (Rh-Ru-Pd) alloy particles of a given composition were obtained. The catalytic performance of the alumina-supported samples was examined in a CO oxidation reaction under prompt thermal aging conditions. It was ascertained that the addition of ruthenium only improves both the initial activity and thermal stability of the catalytic system. The state of each metal in the alloy nanoparticles was characterized by diffuse reflectance UV–vis spectroscopy and X-ray photoelectron spectroscopy.

Photocatalysis entails materials that have specific features for widespread practical applications, including, powerful light absorption, rapid charge transport, an adequate band assembly, and high quantum efficiency in a substantial and definite surface area. The concept of "photochemical potential" is presented on the evidence of using photons as reactants. Now, it can be expressed in the terms "photocatalytic" and "photosynthesis" by referring to all light-induced catalytic activities. These events are mutually spontaneous reactions observed in the allied physical domes. Elementary research practices used to improve the photocatalytic capability of the photocatalysts include innumerable cutting-edge processes such as surface modification, doping with metal or non-metal components, and band gap modification. These techniques can reduce promoted oxidation, photo-induced charge carrier ability, and increase light absorption, but during investigations, the photocatalytic quantum efficiencies and interfacial charge mobilities of the photocatalysts continue to be low and inadequate. It is crucial to create effective photocatalysts that can perform rapid charge separation, high quantum efficiency, and robust light absorption. This succinct analysis examines the timeline of substantial photocatalysis discoveries and offers an overview of current knowledge on the discussed phenomenon. A mathematical expression for photocatalytic degradation was developed and substantiated as a part of this review covering the current needs. It is a forward-looking approach applied to outline the reaction routine and its progression route. This work offers a straightforward outlook for forecasting how well a photocatalytic system will perform in terms of deterioration. A minimum reliance on experimental data and the absence of adjustment factors lead toward a planned approach. The authors provided mathematical equations as a new constraint to analyze mathematical modeling, probability, evaluation of the photocatalytic degradation for revisiting the definition of photocatalysis, analyzing energy bands and energy levels, and finally the Monte Carlo simulation and transpired simulation described. The analogy analysis of electro catalytic water splitting was also included. The probability and apprehensive aspects of a photon have been immersed by photocatalytic suspension and how it will produce an oxidizing agent is further derived through mathematical derivations. Finally, the probability depends only on the photocatalyst performance particularized mathematically.