Fabrication and characterization of flexible and high capacitance supercapacitors based on MnO2/CNT/papers

Flexible paper-based supercapacitors were fabricated using carbon nanotubes (CNTs) and manganese oxides (MnO₂), and their electrochemical properties were characterized in a three-electrode system. CNTs were synthesized via water-assisted chemical vapor deposition (CVD) and dispersed in water using the surfactant sodium dodecylbenzenesulfonate (SDBS). The solution containing dispersed CNTs was simply coated on papers by drop-dry method. MnO₂ was then electrochemically deposited on the CNT-coated papers. The MnO₂/CNT/paper supercapacitors showed high specific capacitance of 540 F/g. Specific energy and specific power were 20 Wh/kg and 1.5 kW/kg, respectively, at current density of 5 A/g in 0.1 M sodium sulfate (Na₂SO₄) aqueous solution. Demonstrated high capacitance of the paper-based electrochemical capacitor makes it a promising candidate for flexible and low-cost energy storage device applications.     

Synergistic improvement of oxygen reduction reaction on gold/cerium-phosphate catalysts

The main challenge in fuel cells lies in improving slow oxygen reduction reaction (ORR) kinetics causing low conversion efficiencies. Here, we introduce the Au/CePO₄-binary nanocomposites as effective oxygen reduction catalysts in alkaline media. The ORR activity comparable with Pt is achieved through the serial 4-electron reduction pathway. The bi-functionality of CePO₄ is suggested to explain the remarkably enhanced activity on the Au/CePO₄ nanocomposites. Significantly, the own catalytic activity of CePO₄ for hydrogen peroxide is demonstrated, validating synergistic effects with Au for complete ORR.     

Triamine‐Based Aromatic Cation as a Novel Stabilizer for Efficient Perovskite Solar Cells

Operational stability of perovskite solar cells has been a challenge from the beginning of perovskite research. In general, humidity and heat are the most well‐known degradation sources for perovskites, requiring ideal design of perovskite chemistry to withstand them. Although triple‐cation perovskite (Cs_0.05(FA_0.85MA_0.15)_0.95Pb(I_0.85Br_0.15)₃) has been already introduced as the stable perovskite material, the high reactivity of methylammonium and formamidinium in the cation sites demands further modification. Herein, 1,2,4‐triazole is suggested as an effective cation solute to improve the performance and stability of perovskite solar cells. 1,2,4‐Triazole is an aromatic cation with low dipole moment that is stable under humidity and heat. It also possesses three nitrogen atoms, forming additional hydrogen bonds in the lattice, stabilizing the material. In this study, the solar cell utilizing 1,2,4‐triazole alloying achieves a power conversion efficiency of 20.9% with superior stability under extreme condition (85 °C/85% of relative humidity (RH), encapsulated) for 700 h. The 1,2,4‐triazole‐alloyed perovskite exhibits reduced trap density and film roughness and enhanced carrier lifetime with electrical conductivity, suggesting an ideal perovskite structure for efficient and stable optoelectronic applications.     

Micro–macro linear piezoelectric motor based on self-moving cell

This paper deals with the development of a piezoelectric linear motor that can control macro and micro movements. Concept of the motor is based on a self-moving cell, which consists of an elastic shell structure and a piezoelectric stack actuator. Three cells are connected in series and by activating piezoelectric actuators in these cells, macro movement can be achieved. Since these cells are fit into a guideway with interference, this motor can possess a high stall force and fail-safe lock. When one piezoelectric actuator is activated by open loop control with hysteresis compensation, micro movement can be obtained. Design of self-moving cell structure, fabrication, and control of the motor for macro and micro movements are explained. The maximum moving velocity of 1.05 mm/s and the maximum force of 4.3 N were observed. The possibility of nano scale movement was demonstrated by taking into account the hysteresis compensation of the piezoelectric actuator.     

Electrochemical properties of tin phosphates with various mesopore ratios

Tin phosphates with various mesopore ratios are synthesized with surfactants as templates. The mesopore ratios of the tin phosphates are controlled by adjusting the surfactant: inorganic precursor ratios. As an anode material for Li-ion batteries, the mesoporous and non-mesoporous mixture with a high mesopore ratio exhibits enhanced cycling stability. Compared with the ∼34% (∼135 mAh g⁻¹) capacity retention after 50 cycles of the non-mesoporous tin phosphate (between 2.5 and 0.001 V), the tin-phosphate anodes with mesopore ratios of 42, 82 and 100% show capacity retentions that are enhanced by more than 50%, showing charge capacities of ∼260, ∼290, and ∼325 mAh g⁻¹, respectively (after 50 cycles). The mesoporous structures may alleviate the large volume change of the Sn nanoparticles embedded in the lithium-phosphate matrix during charge–discharge. Cycling tests of the 100% mesoporous tin phosphate between 0.8 and 0.001 V exhibit no capacity decay: ∼325 mAh g⁻¹ remains after 50 cycles. This is probably because re-oxidation of metallic tin with lithium-phosphate matrix does not occur.     

Design of part family robust-to-production plan variations based on quantitative manufacturability evaluation

This paper presents a systematic method for designing part families whose production costs are insensitive to changes in production plans due to market demand fluctuations. A unified feature-based representation of functional geometry and manufacturability has been developed to manipulate and evaluate part designs. Based on this information and production plans for multiple periods, an optimization-based method provides alternative part designs. The manufacturability of the part designs is quantitatively estimated by the facility cost of the manufacturing system best configured for a given part family and the average cycle time estimated by the discrete event simulation of production scenarios. Redesign suggestions are made on datum definitions of the original parts. Two case studies of a family of prismatic parts and that of turned parts are given to demonstrate the effectiveness of the proposed method. Electronic Publication     

High-performance supercapacitors based on vertically aligned carbon nanotubes and nonaqueous electrolytes

We demonstrate the high performance of supercapacitors fabricated with vertically aligned carbon nanotubes and nonaqueous electrolytes such as ionic liquids and conventional organic electrolytes. Specific capacitance, maximum power and energy density of the supercapacitor measured in ionic liquid were ~75 F g(-1), ~987 kW kg(-1) and ~27 W h kg(-1), respectively. The high power performance was consistently indicated by a fast relaxation time constant of 0.2 s. In addition, electrochemical oxidation of the carbon nanotubes improved the specific capacitance (~158 F g(-1)) and energy density (~53 W h kg(-1)). Both high power and energy density could be attributed to the fast ion transport realized by the alignment of carbon nanotubes and the wide operational voltage defined by the ionic liquid. The demonstrated carbon-nanotube- and nonaqueous-electrolyte-based supercapacitors show great potential for the development of high-performance energy storage devices.