Facile one pot sonochemical synthesis of CoFe2O4/MWCNTs hybrids with well-dispersed MWCNTs for asymmetric hybrid supercapacitor applications

In this study, a facile sonochemical strategy is used for the fabrication of CoFe₂O₄/MWCNTs hybrids as an electrode material for supercapacitor applications. FE-SEM image demonstrates the uniformly well-distributed MWCNTs as well as porous structures in the prepared CoFe₂O₄/MWCNTs hybrids, suggesting 3D network formation of conductive pathway, which can enhance the charge and mass transport properties between the electrodes and electrolytes during the faradic redox reactions. The as-fabricated CoFe₂O₄/MWCNTs hybrids with the MWCNTs concentration of 15 mg (CFC15) delivers maximum specific capacitance of 390 F g⁻¹ at a current density of 1 mA cm⁻², excellent rate capability (275 F g⁻¹ at 10 mA cm⁻²), and outstanding cycling stability (86.9% capacitance retention after 2000 cycles at 3 mA cm⁻²). Furthermore, the electrochemical performance of the CFC15 is superior to those of pure CoFe₂O₄ and other CoFe₂O₄/MWCNTs hybrids (CFC5, CFC10 and CFC20), indicating well-dispersion MWCNTs and uniform porous structures. Also, as-fabricated asymmetric supercapacitor device using the CoFe₂O₄/MWCNTs hybrids as the positive electrode and activated carbon as the negative electrode materials shows the outstanding supercapacitive performance (high specific capacitance, superior cycling stability and good rate capability) for energy storage devices. It delivers a capacitance value of 81 F g⁻¹ at 3 mA cm⁻², ca. 92% retention of its initial capacitance value after 2000 charge-discharge cycles and excellent energy density (26.67 W h kg⁻¹) at high power density (~319 W kg⁻¹).     

Facile synthesis of cauliflower-like cobalt-doped Ni3Se2 nanostructures as high-performance cathode materials for aqueous zinc-ion batteries

Ni₃Se₂ and Co-doped Ni₃Se₂ cauliflower-like nanostructures are synthesized using a simple and feasible electrochemical deposition technique. Electrochemical measurements of the resultant nanostructures in 1 M KOH electrolyte solution revealed that the energy storage performance of the cauliflower-like Ni₃Se₂ nanostructures was considerably improved by cobalt doping. Particularly, 6 wt% Co-doped Ni₃Se₂ electrodes exhibited remarkable high specific capacity (179.34 mAh g⁻¹) and excellent stability with capacity retention of 85.9% over 1000 cycles because of their high electrical conductivity. Furthermore, to verify the feasibility of the optimized Co-doped Ni₃Se₂ electrodes for practical applications, Zn ion batteries were constructed by using a Zn plate as the anode and the Co-doped Ni₃Se₂ nanostructures as the cathode. The constructed Zn ion battery achieved high energy and power densities of 199.34 W h kg⁻¹ and 24,510 W kg⁻¹ at the current densities of 1 and 20 A g⁻¹, respectively. In addition, up to 2.2 electrons per formula unit of Ni₃Se₂ were successfully utilized, indicating considerably higher utilization of Ni²⁺/Ni³⁺ redox sites by Co doping the selenite. This work demonstrated an effectual strategy for rational design of highly robust, low-cost flexible electrodes for energy storage devices.     

Systematic study of optoelectronic and transport properties of cesium lead halide (Cs2PbX6; X=Cl,Br, I) double perovskites for solar cell applications

A systematic density functional theory investigation of Cs₂PbX₆ (X = Cl, Br, I) double perovskites is presented. The lattice constants are computed after structure optimization and using Birch-Murnaghan equations, which agree to the experimental literature. The mechanical stability conditions satisfy Born criteria, and the ductile nature is evidenced by the calculated Poisson's (v) and Pugh's ratios (B₀/G) because all three double perovskites exhibit values higher than the respective critical values v = 0.26 and B₀/G = 1.75. A detailed study of the optoelectronic properties reveals these double perovskites as promising candidates for future optical devices due to their direct band gaps (within 0.45–2.54 eV) and large absorption coefficients 5.95 × 10⁵ cm⁻¹, which are suitable for solar cell applications. ZT calculations demonstrate minute variations within 200–800 K and computed parameter values are quite favorable for thermoelectric applications of these materials in the future. A p-type semiconducting nature is predicted by the computed thermoelectric properties. Additionally, computed refractive indices show Cs₂PbBr₆ and Cs₂PbI₆ exhibiting super-luminescent properties in the UV range. Therefore, the studied double perovskites provide further interest for future energy conversion and photonic based technologies.     

Discrete‐time sector based hands‐off control for nonlinear system

This article presents a hands‐off control design for discrete‐time nonlinear system with a special type of nonlinear sector termed as “discrete‐time sector.” The design method to define the boundary of a discrete‐time sector is done with control‐Lyapunov function. The generalization of nonlinear system is viewed in the perspective of a comparison function. By means of a proposed sector, a switching control is designed such that no control action is experienced inside the sector thus, saving unnecessary control efforts. However, to study the robustness for discrete‐time system, a hands‐off control is modified to ensure the monotonic decrease in the energy of the system. Finally, the proposed approach is verified with the simulation results.     

Self-Assembly of Proteinaceous Shells around Positively Charged Gold Nanomaterials Enhances Colloidal Stability in High-Ionic-Strength Buffers

The enzyme lumazine synthase (LS) has been engineered to self-assemble into hollow-shell structures that encapsulate unnatural cargo proteins through complementary electrostatic interactions. Herein, we show that a negatively supercharged LS variant can also form organic–inorganic hybrids with gold nanomaterials. Simple mixing of LS pentamers with positively charged gold nanocrystals in aqueous buffer spontaneously affords protein-shelled gold cores. The procedure works well with differently sized and shaped gold nanocrystals, and the resulting shelled complexes exhibit dramatically enhanced colloidal stability over a wide range of pH (4.0–10.0) and at high ionic strength (up to 1 m NaCl). They are even stable over days upon dilution in buffer. Self-assembly of engineered LS shells in this way offers an easy and attractive alternative to commonly used ligand-exchange methods for stabilizing inorganic nanomaterials.     

用于水质净化的氧化石墨烯膜研究进展

氧化石墨烯膜具有超高的水通量、可控的层间距以及卓越的分离性能，这些优异的特性使氧化石墨烯膜有望成为新一代膜材料并用于水环境中物质的精确分离。对氧化石墨烯膜的研究已经取得了许多重要的成果，本文系统地阐述了用于水质净化的氧化石墨烯膜的结构特性和构效关系，总结了氧化石墨烯膜典型的制备方法，重点介绍了氧化石墨烯膜的改性方式，概述了氧化石墨烯膜在多种水环境中的应用，总结并展望了氧化石墨烯膜的发展方向，为设计和合成高性能氧化石墨烯膜用于水质净化提供新的思路。     

OMS-2催化剂成型工艺研究及其在印染废水处理中的应用

以OMS-2粉体催化剂为基础,对催化剂进行挤出成型,考察粘结剂种类、粘结剂用量、润滑剂和孔结构改进剂用量、焙烧温度对成型催化剂机械强度的影响。得到最佳成型工艺条件为,粘结剂硅溶胶用量为OMS-2粉体催化剂质量的105%～110%、辅助粘结剂纳米ZrO_2用量为OMS-2粉体催化剂质量的30%～35%、润滑剂田菁粉用量为OMS-2粉体催化剂质量的2. 5%～3. 0%、孔结构改进剂柠檬酸用量为OMS-2粉体催化剂质量的5%～6%,焙烧温度450℃。成型后催化剂机械强度可达150 N·cm~(-1),满足工业化应用对催化剂强度的要求。将成型催化剂应用于催化湿式氧化印染废水处理,经过432 h活性评价时间,COD平均去除率约91. 6%,反应结束后催化剂结构完整,平均机械强度约144 N·cm~(-1),表现出良好的水热稳定性。     

Achieving both large piezoelectric constant and high Curie temperature in BiFeO3-PbTiO3-BaTiO3 solid solution

The high-temperature and high-performance piezoelectric ceramics are required urgently in the petrochemical, automotive, and aerospace industries. In this work, the (0.85-x)BiFeO₃-xPbTiO₃-0.15BaTiO₃ (BF-PT-BT, x = 0.21, 0.22, 0.23, 0.24 and 0.25) piezoelectric ceramics with both high Curie temperature and large piezoelectric constant d₃₃ were presented. X-ray diffraction analysis shows that BF-PT-BT ceramics exhibit dominant perovskite structure with the coexistence of tetragonal (T) and rhombohedral (R) phases. The c/a ratio, Curie temperature, piezoelectric constant, dielectric constant and loss of the BF-PT-BT ceramics for x = 0.23 are 1.06, 546 °C, 222 pC/N, 545 and 0.013, respectively. Room temperature piezoelectric constant of BF-PT-BT ceramics is much higher than those of PbTiO₃, PbNb₂O₆ and other ABO₃ perovskite compounds (BaZrO₃, Bi(Zn, Ti)O₃, PbZrO₃ and Pb(Mg, Nb)O₃) modified ternary BiFeO₃-PbTiO₃ ceramics with similar Curie temperatures. The piezoelectric constant is almost unchanged after BF-PT-BT ceramics was annealed at 450 °C for 30 min, which is due to the stable switched non-180° domain and transformed R phase by annealing treatment.     

Adaptive control of unactuated dynamical systems through interconnections: Stability and performance guarantees

This article studies control and performance enforcement for a class of uncertain dynamical systems that consist of actuated and unactuated portions physically interconnected to each other. The proposed approach stabilizes the overall interconnected system in the presence of unknown physical interconnections as well as system uncertainties. Performance guarantees are enforced, individually, on the actuated as well as unactuated portions of the interconnected system via this approach. For enforcing these performance guarantees, a set-theoretic model reference adaptive control approach is used, in conjunction with linear matrix inequalities, to restrict the respective system error trajectories of the actuated and unactuated dynamics inside a priori, user-defined compact sets. The efficacy of the proposed approach is demonstrated using simulations.     

超级电容器用solvent-in-salt型电解液的研究进展

Solvent-in-salt (SIS)型电解液作为一类新型超浓缩电解液，主要由水或者有机溶剂和易溶盐组成，具有溶液溶剂化程度小、自由溶剂分子少、电化学窗口宽、电化学稳定性高等特点，在超级电容器中显示了独特的优势并展现了良好的应用前景。本文重点综述了SIS型电解液的原理和优势，梳理了近年来SIS作为超级电容器电解液的研究进展，总结了其存在的问题，同时展望了SIS型电解液未来的发展方向。