环氧树脂/碳钢电极在硫酸溶液中的半导体导电行为

采用电位-电容测试和Mott-Schottky分析技术研究了环氧树脂/碳钢电极在0.5 mol·L-1硫酸中腐蚀失效过程中的半导体导电行为. 环氧树脂在刚刚浸入溶液时(10 min)为绝缘体, 随着浸泡时间延长, 由于离子的腐蚀,环氧树脂外层逐渐转变为n 型半导体. 半导体层中的载流子密度随着浸泡时间的延长而增大,载流子由浸泡7 h约1010 cm-3增大到48 h的约1012 cm-3数量级, 浸泡48 h 以内涂层没有完全转变为半导体, 碳钢表面包括环氧树脂层在浸泡7-48 h 期间为MIS(metal-insulator-semiconductor)结构. 此MIS 结构空间电荷层在-0.5 - 0.5 V内处于反型状态, 反型层内的载流子为空穴. 在较低频率下测得空间电荷层电容为反型层电容和耗尽层电容的串联电容, 随电位升高而减小;较高频率下测得空间电荷层电容仅为耗尽层电容, 不随极化电位变化. 该MIS结构的电位-电容特性曲线与理想MIS结构相比发生了阳极漂移.     

Co(OH)2-combined carbon-nanotube array electrodes for high-performance micro-electrochemical capacitors

We have investigated binder-free Co(OH)₂-combined carbon-nanotube (CNT) array electrodes using anodized aluminum oxide (AAO) templates for micro-electrochemical capacitors. It is shown that compared to the capacitors fabricated with CNT only electrodes (6.3 F/cm³ at 100 mV/s), those with the Co(OH)₂-combined CNT array electrodes produce much higher capacitance (12.74 F/cm³ at 100 mV/s) together with superior high-rate capacitance. The improved electrochemical behavior is explained in terms of high capacitance of amorphous Co(OH)₂ electrode and the use of CNT arrays as effective current collector.     

储能薄膜电容器介电高分子材料

高功率密度、高充放电效率以及超长使用寿命等特点是聚合物薄膜电容器能够广泛应用于电动汽车、智能电网等各类电子电气领域中的重要原因。其中,介电高分子材料因其质轻、击穿强度高、易大规模加工等优点赋予了薄膜电容器更多的可能性。但同时,介电高分子的介电常数普遍较低,导致所制备的电容器能量密度偏低因而不能更好地适应设备小型化轻型化的要求。本文概述了电介质以及薄膜电容器的基本原理以及性能参数,着重介绍了以储能为主要研究方向的介电高分子材料,主要包括聚合物基纳米复合介电高分子、偶极玻璃聚合物、交联型介电高分子以及多组分全有机介电高分子。最后对介电高分子在制备性能优异的储能电容器过程中面临的多重挑战和潜在机遇进行了总结。     

Pumpkin‐Derived Porous Carbon for Supercapacitors with High Performance

Pumpkin has been employed for the first time as a renewable, low‐cost precursor for the preparation of porous carbon materials with excellent performance. Unlike most other precursors, pumpkin is rich in sugars and starch, and it has advantageous properties for large‐scale production. The as‐prepared materials adopted a unique morphology that consisted of numerous fused sphere‐like carbon grains with a high specific surface area (2968 m² g^?1), abundant micro and mesopores, and excellent electrochemical properties. The pumpkin‐derived activated carbon (PAC) material not only exhibited a high specific capacitance of 419 F g^?1, but also showed considerable cycling stability, with 93.6 % retention after 10 000 cycles. Moreover, a symmetrical supercapacitor that was based on PAC showed a high energy density of 22.1 W h kg^?1 in aqueous electrolyte. These superior properties demonstrate that PAC holds great promise for applications in electrochemical energy‐storage devices.     

Correspondence between the Frumkin and Alekseev-Popov-Kolotyrkin models at the adsorption of neutral organic molecules

By the example of a system Hg/(H₂O + xM NaF + yM n-C₄H₉OH) for four x values (0.01, 0.03, 0.1, and 0.3) in combination with six different y values (in a range from 0.05 to 0.8), an assumption on the simultaneous fulfillment of the classical model of the diffuse layer and the model of two parallel capacitors supplemented by the Frumkin isotherm is analyzed. It is shown that the classical theory of the diffuse layer agrees with experimental data on the capacitance in this system and also on the adsorption of secondary butanol not only near the zero-charge potential but also in the vicinity of adsorption-desorption peaks where the electrode charge reaches absolute values of 6–10 μC/cm². At the same time, the experimental differential capacitance curves in this system are well described by the model of two parallel capacitors supplemented by the Frumkin isotherm (the Frumkin model) for all supporting-electrolyte concentrations. However, this model is far less accurate in describing the calculated curves of the dense-layer differential capacitance, which contradicts the straightforward physical basis of the Alekseev-Popov-Kolotyrkin model. To resolve this contradiction, further studies with the use of molecular models are necessary.     

Review of the role of ionic liquids in two-dimensional materials

Ionic liquids (ILs) are expected to be used as readily available “designer” solvents, characterized by a number of tunable properties that can be obtained by modulating anion and cation combinations and ion chain lengths. Among them, its high ionicity is outstanding in the preparation and property modulation of two-dimensional (2D) materials. In this review, we mainly focus on the ILs-assisted exfoliation of 2D materials towards large-scale as well as functionalization. Meanwhile, electric-field controlled ILs-gating of 2D material systems have shown novel electronic, magnetic, optical and superconducting properties, attracting a broad range of scientific research activities. Moreover, ILs have also been extensively applied in various field practically. We summarize the recent developments of ILs modified 2D material systems from the electrochemical, solar cells and photocatalysis aspects, discuss their advantages and possibilities as “designer solvent”. It is believed that the design of ILs accompanying with diverse 2D materials will not only solve several scientific problems but also enrich materials design and engineer of 2D materials.     

Radical Covalent Organic Frameworks: A General Strategy to Immobilize Open‐Accessible Polyradicals for High‐Performance Capacitive Energy Storage

Ordered π‐columns and open nanochannels found in covalent organic frameworks (COFs) could render them able to store electric energy. However, the synthetic difficulty in achieving redox‐active skeletons has thus far restricted their potential for energy storage. A general strategy is presented for converting a conventional COF into an outstanding platform for energy storage through post‐synthetic functionalization with organic radicals. The radical frameworks with openly accessible polyradicals immobilized on the pore walls undergo rapid and reversible redox reactions, leading to capacitive energy storage with high capacitance, high‐rate kinetics, and robust cycle stability. The results suggest that channel‐wall functional engineering with redox‐active species will be a facile and versatile strategy to explore COFs for energy storage.     

Effects of gamma irradiation on electrical parameters of metal–insulator–semiconductor structure with silicon nitride interfacial insulator layer

The effects of gamma irradiation on electrical parameters of Au/Si₃N₄/n-Si (MIS) structure were investigated by using the capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. The MIS structure was irradiated using gamma-radiation source at a dose rate of 0.69?kGy/h. The C–V and G/ω–V measurements were carried out at a total dose range of 0–100?kGy for five different frequencies (1, 10, 100, 500 and 1000?kHz). The obtained results showed that the C and G/ω values decrease with the increasing radiation dose due to the irradiation-induced defects at the interface. Also, the observed decrease in the C and G/ω values with the increasing frequency was explained on the basis of interface states (N_ss). The values of series resistance (R_s) increase with the increasing radiation dose. To obtain the real capacitance and conductance of the capacitor, the measured values of C and G/ω were corrected to eliminate the effect of series resistance. The values of N_ss were determined by using the conductance method and were decreased with the increasing radiation dose.     

Polymer nanocomposites for electrical energy storage

This review highlights the frontier scientific research in the development of polymer nanocomposites for electrical energy storage applications. Considerable progress has been made over the past several years in the enhancement of the energy densities of the polymer nanocomposites via tuning the chemical structures of ceramic fillers and polymer matrix and engineering the polymer–ceramic interfaces. This article summarizes a range of current approaches to dielectric polymer nanocomposites, including the ferroelectric polymer matrix, increase of the dielectric permittivity using high‐permittivity ceramic fillers and conductive dopants, preparation of uniform composite films based on surface‐functionalized fillers, and utilization of the interfacial coupling effect. Primary attentions have been paid to the dielectric properties at different electric fields and their correlation with film morphology, chemical structure, and filler concentration. This article concludes with a discussion of scientific issues that remain to be addressed as well as recommendations for future research. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1421–1429, 2011