Nanodendrites of platinum-group metals for electrocatalytic applications

Developing highly efficient and durable catalysts for future electrochemical and energy applications is one of the main subjects of current studies in renewable energy generation. In the past several years, researchers have developed Pt-based alloy electrocatalyst nanomaterials that exhibit promising electrocatalytic properties for various electrochemical applications. The efficient structural and morphological control of Pt-based alloy materials plays a decisive role in achieving these enhanced electrocatalytic properties. The present review article emphasizes the recent progress and important developments in the synthesis and electrocatalytic applications of Pt-group-based nanodendrite materials. The following review will help the exploration and development of better catalysts for practical applications and aims to elucidate the nanodendrite structure of Pt-group metals.

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ITO deposited by pyrosol for photovoltaic applications

The goal of this work is to investigate morphology, electrical and optical properties of indium-tin-oxide (ITO) deposited by pyrosol on glass and Si substrates at different temperatures and to implement such layers for the processing of Si-based solar cells. The influence of the methanol/H₂O ratio on general properties of ITO was investigated. Atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission spectra, ellipsometry and resistivity measurements were used for the analysis. It is shown that properties of ITO layers depend dramatically on the substrate used. It is shown that the resistivity of ITO layers deposited on a glass substrate is higher up to 2.5 times, compared to that of ITO layers deposited on a Si substrate at the same conditions, but in both cases decreases if the deposition temperature increases. Moreover, ITO layers deposited on a glass substrate are more flat and their refractive indexes are always lower for all deposition temperatures. An increase of the H₂O concentration in a film-forming solution leads to a decrease of the ITO film resistivity and to a slight increase of the roughness. An application of pyrosol deposited ITO films as the top transparent electrodes for the (p⁺nn⁺)Si and heterojunction ITO/n-Si solar cells is demonstrated.     

ITO coated quartz fibers for heat radiative applications

Radiation heat transfer through fibrous materials is very strong at high temperatures (up to 1000 °C). Indium tin oxide (ITO) thin films were sol-gel deposited onto the surfaces of fibers to reduce the radiation heat transfer as radiation reflective coatings. SEM, XRD and FT-IR techniques were used to characterize the microstructure and performance of films. Results show that ITO thin film is uniformly deposited on fibers with a thickness of about 200 nm and can be used to apply a radiative reflective coating. Moreover, the efficiency of radiation reflective properties of films is improved as the annealing temperature increases. Results prove that ITO film is an excellent candidate to reduce the radiation heat transfer as radiation reflective coatings on fibrous materials.     

Peptide nanotube-modified electrodes for enzyme-biosensor applications

The fabrication and notably improved performance of composite electrodes based on modified self-assembled diphenylalanine peptide nanotubes is described. Peptide nanotubes were attached to gold electrodes, and we studied the resulting electrochemical behavior using cyclic voltammetry and chronoamperometry. The peptide nanotube-based electrodes demonstrated a direct and unmediated response to hydrogen peroxide and NADH at a potential of +0.4 V (vs SCE). This biosensor enables a sensitive determination of glucose by monitoring the hydrogen peroxide produced by an enzymatic reaction between the glucose oxidase attached to the peptide nanotubes and glucose. In addition, the marked electrocatalytic activity toward NADH enabled a sensitive detection of ethanol using ethanol dehydrogenase and NAD+. The peptide nanotube-based amperometric biosensor provides a potential new tool for sensitive biosensors and biomolecular diagnostics.     

Inkjet-printing of indium tin oxide (ITO) films for transparent conducting electrodes

Indium-tin-oxide (ITO) films have been prepared by inkjet-printing using ITO nanoparticle inks. The electrical and optical properties of the ITO films were investigated in order to understand the effects of annealing temperatures under microwave. The decrease in the sheet resistance and resistivity of the inkjet-printed ITO films was observed as the annealing temperature increases. The film annealed at 400 °C showed the sheet resistance of 517 Ω/sq with the film thickness of ∼580 nm. The optical transmittance of the films remained constant regardless of their annealing temperatures. In order to further reduce the sheet resistance of the films, Ag-grid was printed in between two layers of inkjet-printed ITO. With 3 mm Ag-grid line-to-line pitch, the Ag-grid inserted ITO film has the sheet resistance of 3.4 Ω/sq and the transmittance of 84% after annealing at 200 °C under microwave.     

Urania-yttria solid solution electrodes for high-temperature electrochemical applications

Measurements of total electrical conductivity on fluorite-type U₃O₈-Y₂O₃ (Sc₂O₃) solid solutions have been made as a function of temperature and U/Y(Sc) ratio. The following compositions were studied: (U_0.7Y_0.3)O_2+x , (U_0.6Y_0.4)O_2+x , (U_0.5Y_0.5)O_2+x , (U_0.45Y_0.55)O_2+x , (U_0.4Y_0.6)O_2+x , (U_0.35Y_0.65)O_2+x , (U_0.3Y_0.7)O_2−x , (U_0.5Sc_0.5)O_2+x and (U_0.38Sc_0.62)O_2+x . Preliminary measurements on the latter two compositions were carried out for comparison purposes. The maximum conductivity value occurred for the U₃O₈-Sc₂O₃ solid solutions, and for (U_0.7Y_0.3)O_2+x in the U₃O₈-Y₂O₃ system. The conductivity in these fluorite-type solid solutions is mainly electronic, the conduction mechanism being hopping-type. The energy of activation lay between 25 and 40 kJ mol⁻¹. The (U_0.3Y_0.7)O_2−x composition appeared to be an ionic conductor with an activation energy of ∼110 kJ mol⁻¹ below 800 to 850° C. The diffusion of cations of U₃O₈-Y₂O₃ into ZrO₂-Y₂O₃ was studied during passage of current: no observable diffusion occurred over the period of current passage (384 h). Attempts were made to determine the anionic contribution to the total conductivity in U₃O₈-Y₂O₃ solid solutions using the blocking electrode technique. Results indicated that complete isolation of the specimen-blocking electrode (YSZ) interface from the ambient gases is necessary if such measurements are to be reliable. The diffusion coefficients calculated from the conductivity data using the Nernst-Einstein relation were two orders of magnitude higher than those obtained by a direct method.     

溶胶-凝胶法制备ITO薄膜研究进展

概述了近年来国内外溶胶-凝胶法(Sol-Gel)制备ITO薄膜的研究状况,对Sol-Gel法制备ITO薄膜工艺做了简要介绍,重点讨论了Sol-Gel法制备ITO薄膜的溶胶体系,分析比较了有机醇盐、无机盐以及掺入ITO粉末方法体系的优缺点,最后讨论了甩膜法、提拉法及平铺法在Sol-Gel法制备ITO薄膜中镀膜的应用.指出Sol-Gel法是一种高效可行的制备ITO薄膜的方法,有着广阔的应用前景.     

Characteristics of ITO films with oxygen plasma treatment for thin film solar cell applications

The influence of oxygen plasma treatment on the electro-optical and structural properties of indium-tin-oxide films deposited by radio frequency magnetron sputtering method were investigated. The films were exposed at different O₂ plasma powers and for various durations by using the plasma enhanced chemical vapor deposition (PECVD) system. The resistivity of the ITO films was almost constant, regardless of the plasma treatment conditions. Although the optical transmittance of ITO films was little changed by the plasma power, the prolonged treatment slightly increased the transmittance. The work function of ITO film was changed from 4.67 eV to 5.66 eV at the plasma treatment conditions of 300 W and 60 min.     

Optical characterization of indium-tin-oxynitride fabricated by RF-sputtering

Indium-tin-oxynitride (ITON) and indium-tin-oxide (ITO) thin films have been fabricated by r.f. sputtering from an indium-tin-oxide target in a plasma containing N₂ and Ar gases, respectively. The properties of films grown at two different plasma pressures were examined just after deposition and after annealing. Although the electrical properties of these films were improved after annealing, the properties of the ITON films were still inferior to those of the ITO films. The resistivity of the ITON films after annealing was reduced by a factor of two for the film at the higher plasma pressure, but the carrier concentration was almost the same. The ITON films fabricated at low pressure exhibited a significant blue shift in transmittance, which was not related to the increase carrier concentration after annealing.     

Electroluminescence: enhanced injection using ITO electrodes coated with a self assembled monolayer

In a typical organic bilayer electroluminescent device the hole injecting electrode is almost invariably ITO glass, but a number of electron injecting metal electrodes are possible. Unfortunately the low work function materials used readily oxidise and restrict the lifetime of the device. It is known that appropriate monolayers can change the work function of a solid and also that phosphonic acids can form self assembled monolayers on ITO glass. Using an ITO glass electrode coated with a self assembled monolayer of an electron accepting phosphonic acid (2-chloroethanephosphonic acid) and aluminium as the electron injecting electrode, it was found that the threshold voltage was significantly reduced to the same value as achieved with the less stable Mg:Ag electrode. The use of such modified ITO electrodes would obviate the use of highly reactive metal electrodes and help to overcome one of the factors which limit device lifetime.     

Crystallization and electrical properties of ITO:Ce thin films for flat panel display applications

ITO and ITO:Ce films were deposited by DC magnetron sputtering using an ITO (SnO₂: 10 wt.%) target and CeO₂ doped ITO (CeO₂: 0.5, 3.0, 4.0 and 6.0 wt.%) ceramic targets, respectively, on unheated non-alkali glass substrates (corning E2000). The as-deposited films were annealed at 200 °C in an Ar atmosphere at a pressure of 1 Pa. The crystallization temperature of the ITO film was increased by introducing Ce atoms because they decrease the level of crystallinity. It was also confirmed that the etching rate, surface morphology and work function were improved by the addition of Ce atoms despite there being increased resistivity. The current voltage (I-V) characteristics of the OLED devices deteriorated with increasing Ce content in the ITO anode, which was attributed to a decrease in carrier density despite there being a high work function. Therefore, the carrier density is one of the most important factors that determine the turn-on voltage for OLED applications.     

NiFe-植酸复合物的室温制备及其全解水电催化性能

制备高稳定性、高活性双功能催化剂用于全解水制氢是氢能源大规模商业化应用的重要环节之一。本文以植酸(PA)、六水合氯化铁(FeCl₃·6H₂O)和六水合氯化镍(NiCl₂·6H₂O)为原料,采用两步室温浸渍法在泡沫镍(NF)上制备了片状无定形植酸-镍铁双金属复合材料(NiFe-PA)。采用线性扫描伏安法(LSV)考察了NiFe-PA修饰NF电极(NiFe-PA/NF)在碱性条件(1.0 mol/L KOH)的电解水催化性能。实验结果表明：由于NiFe双金属之间的协同效应,NiFe-PA/NF作为双功能催化剂显示出优越的析氧和析氢性能。NiFe-PA/NF电极在50 mA·cm^-2电流密度下析氧反应的过电位仅需220 mV;在10 mA·cm^-2电流密度下的析氢反应的过电位为135 mV。将NiFe-PA/NF组装成双电极系统用于全解水,达到10 mA·cm^-2电流密度的电池电压仅需1.61 V,低于贵金属催化剂体系RuO₂     

柔性储能电池电极的设计、制备与应用EI北大核心CSCD

随着便携式、可穿戴电子器件的迅速发展,柔性储能器件的研究逐渐转向微型化、轻柔化和智能化等方向。同时人们对器件的能量密度、功率密度和力学性能有了更高的要求。电极材料作为柔性储能器件的核心部分,是决定器件性能的关键。柔性储能电子器件的发展,又迫切需要新型电池技术和快速、低成本且可精准控制其微结构的制备方法。因此,柔性锂/钠离子电池、柔性锂硫电池、柔性锌空电池等新型储能器件的研发成为目前学术界研究的热点。本文论述了近年来柔性储能电池电极的研究现状,着重对柔性电极材料的设计(独立柔性电极和柔性基底电极)、不同维度柔性电极材料的制备工艺(一维材料、二维材料和三维材料)和柔性储能电极的应用(柔性锂/钠离子电池、柔性锂硫电池、柔性锌空电池)进行对比分析,并对电极材料的结构特性和电化学性能进行了讨论。最后,指出了柔性储能器件目前所面临的问题,并针对此类问题展望了柔性储能器件未来的重点在于新型固态电解质的研发、器件结构的合理设计及封装技术的不断优化。     

Evaluation of transient responses of ammonia-selective potentiometric electrodes for quantitative applications.

An error-compensating, predictive kinetic method is adapted and evaluated for quantitative applications based on transient responses from an ammonia-selective electrode. Transient data collected during the early part of the electrode response are used with a curve-fitting method and appropriate mathematical models to predict the signal that would be measured if the response were monitored to equilibrium. Several different theoretical and empirical models were evaluated, and all but one of the models tested permitted reliable prediction of equilibrium potentials for most responses. Predicted values of equilibrium signal were close to measured values and exhibited the expected logarithmic dependence on ammonia concentration in the range from 0.1 to 100 mmol/L. Slopes of calibration plots E infinity vs log C, varied from about 50.5 to 65.0 mV per decade with an average value of 56.9 +/- 4.2 mV per decade. Quantitative data are used to rank the different models in terms of their utility for kinetic-based determinations of ammonia by using the ammonia-selective electrode.     

Optical sensor with transparent conductive oxides electrodes for microposition detection applications

This paper presents an optical sensor structure for microposition detection application using transparent electrodes of indium doped ZnO (IZO). The optical microsensor consists of two linear arrays of metal - semiconductor - metal (MSM) silicon photodetectors with IZO transparent electrodes integrated with a polymer optical waveguide.IZO layers with a thickness of 460-580 nm have been deposited by dc magnetron sputtering technique on silicon epitaxial wafers of 30-50 Ω cm resistivity and a thickness of 23 µm. Due to their high optical transmittance (> 90%) over the 0.4-0.9 µm spectral range, these layers contributed to an increased responsivity of the MSM photodiode structure of about 0.34 A/W, thus improving the optical position microsensor sensitivity.     

Study of YSZ-based electrochemical sensors with oxide electrodes for high temperature applications

Potentiometric sensors based on yttria stabilized zirconia (YSZ) with WO₃ as sensing electrode were fabricated using either Pt or Au electrodes. The sensors were studied in the temperature range 550–700°C in the presence of different concentrations (300-1000 ppm) of NO₂ and CO in air. The response to NO₂ was very stable with fast response time (20-40 s). The best sensitivity (18.8 mV/decade) using Pt electrodes was observed at 600°C. At the same temperature a cross-sensitivity (-15 mV/decade) to CO gas was also noticed. The response to CO was decreased (-4 mV/decade) using Au electrode. The role played by WO₃ on the sensing electrode was discussed.     

ITO及WO3在电解液中的交流阻抗特性

采用表面过程法拉第阻纳表达式方法与等效电路方法，研究透明ITO平面电极及带WO3薄膜层的ITO平面电极处于1mol LiClO4丙烯碳酸酯电解液中的电化学阻抗谱．分析显示WO3薄膜层有效地阻止了表面吸附参量对ITO电极反应的影响，使电极反应仅受电极电位的影响，并且随WO3薄膜在电解液中浸泡时间的增加，WO3薄膜的常相位角元件的特性最终回归为电容效应．