纯铜、纯钴电极和铜钴合金电极在碱性介质中的光电化学研究

用动电位伏安法对纯铜电极、纯钴电极以及含钴量5.1%、9.7%、15%、25%和40%的铜钴合金电极在硼砂—硼酸缓冲溶液(pH8.5)中的光电化学行为进行了研究。纯铜电极、纯钴电极和铜钴合金电极均显示P-型光响应,纯铜电极的光响应来自Cu2O,纯钴电极的光响应主要来自Co3O4,铜钴合金电极的光响应来自Cu2O和Co3O4的共同作用。纯铜电极在阳极氧化过程中存在着Cu的阳极溶解和电极表面生成Cu2O膜的反应,温度升高有利于Cu2O膜的生成,除氧与否影响纯铜电极的成膜反应。纯钴电极电位正向扫描时不显示光响应,负向扫描时显示阴极光电流。铜钴合金电极的光响应随含钴量而变化。     

BTA系列缓蚀剂对铜缓蚀作用的光电化学比较

采用光电化学方法将不同浓度的BTA(苯并三氮唑)及其衍生物在硼砂缓冲溶液(pH9．2)中对铜电极的缓 蚀性能及机理作了比较研究。研究发现,羧基类BTA衍生物(4CBTA、5CBTA、CBT-1)和酯类BTA衍生物(CBTME、 CBTBE,含BTA)对铜的缓蚀作用机理不同。前者对铜的作用主要是缓蚀剂在电极表面形成的膜能促使Cu2O膜不 断增厚,进而起到缓蚀作用,体现在一定浓度的缓蚀剂作用下,电位负向扫描过程中阴极光电流明显增大,缓蚀效 果可用阴极光电流的大小来评定,阴极光电流越大,缓蚀效果越好;后者对铜的作用主要是通过缓蚀剂在电极表面 形成的膜比较致密地阻止了溶液中的O2-进入到金属表面,改变了铜表面的Cu2O膜的化学计量比,体现在一定浓 度的缓蚀剂作用下,电位正向扫描过程中光响应由p型转为n型,缓蚀效果可用阳极光电流的大小来评定,阳极光 电流越大,缓蚀效果越好。     

铜电极在缓蚀协同作用过程中光电化学行为的转变

采用光电化学方法考察了铜缓蚀剂苯并三唑(BTA)分别与咪唑(IM)和8-羟基喹啉(HQ)的复配效果。实验表明:在电位正向扫描过程中,高浓度的IM能使铜电极的光响应从p-型转变为n-型,而HQ却不能使铜电极的光电流发生转型;在电位负向扫描过程中,HQ能使铜电极产生的阴极光电流峰值明显增大。IM和HQ分别与BTA复配后导致铜电极产生不同的光电化学响应行为。采用MM2分子力学程序和PPP-SCF量子化学方法计算了它们的分子结构参数,分析讨论了它们之间的缓蚀协同作用:IM能够促进BTA在铜表面的吸附和成膜,而HQ能够维持铜表面[Cu(I)BTA]膜的致密性和完整性。     

掺杂型夹层光电极的光催化作用 Ⅰ.电极特性及其光解H_2O能力初探

以掺杂多晶n-TiO_2(Au)~(**)为电极表层,以n-GaAs为电极底层,以S~(2-)/S_x~(2-)做夹层液制成夹层光阳极。Pt做阴极。饱和甘汞电极做参比电极。阴阳两室均用1MNaOH做支持电解质溶液组成光电解池。实验发现夹层光阳极的光电转换能力比单独的掺杂型多晶n-TiO_2(Au)光阳极大得多,其稳定性比单独n-GaAs电极好。又发现多晶n-TiO_2·Ti~(3 )(Au)做夹层电极的表层,用氙灯照射时,无需外加偏压便可观察到阳极释O_2,阴极释H_2。初步讨论了光电裂解H_2O的机理。     

直接甲醇燃料电池所用催化剂和膜电极工艺研究进展

直接甲醇燃料电池由于其高效的能量转化效率、清洁环保、体积小、重量轻、可低温快速启动等优点,在未来将得到广泛应用.介绍了直接甲醇燃料电池工作原理及核心部件的相关研究进展,包括阳极催化剂、阴极催化剂和膜电极工艺.阐述了电极催化剂的工作原理,并按负载的活性金属组分的不同,对电极催化剂进行分类总结.阳极贵金属基催化剂中,Pt分别与Ru、Co、Fe、Ni的合金催化剂表现出比纯Pt催化剂更优越的性能.阴极贵金属基催化剂中,Pt-Fe体系催化效果较好.研究分析表明,贵金属基合金纳米结构均匀分散与载体上,产生更高的电化学活性表面积和更低的电荷转移电阻,催化剂稳定性与催化活性较大提高.非贵金属基催化剂则是以氧化物及过渡金属为代表取代Pt,展现较好性能,但还存在催化效率不足的问题.膜电极工艺流程较为成熟固定,活化工艺及质子交换膜有待深入研究.     

聚丁基紫精修饰的p-Si光电极

用电沉积法将聚丁基紫精(PBV)覆盖干p-Si光电极表面进行修饰,提高了稳定性。在NaClO_4-NaTFA(pH=2)溶液中测量了经修饰后的光电极的循环伏安图,式量电位(formal potential)E_f为—0.23V(VS. SCE),亏电位(underpotential)为0.25V。循环扫描240次后(扫描速度50mV/s),光电流大致不变。而未经修饰的p-Si光电极,在同样溶液中进行循环伏安测量,光电流下降很快。     

BTA衍生物对铜缓蚀作用的光电化学研究

研究了铜电极在含ＢＴＡ及其系列ＣＢＴＭＥ,ＣＢＴＢＥ三种缓蚀剂的硼砂缓冲溶液中的光电化学行为。当溶液中含有一定量的ＢＴ,ＣＢＴＭＥ和ＣＢＴＢＥ时,电位在正向扫描过程中,电极光响应由ｐ型转变为ｎ型。ＢＴＡ的缓蚀作用优于ＣＢＴＭＥ和ＣＢＴＢＥ。一定比例的ＢＴＡ和ＣＢＴＭＥ复配后对铜的缓蚀作用有协同效应。可以用光电化学方法评价铜缓蚀剂的效果。交流阻抗法测得的结果与光电化学方法相符。     

银汞合金电极的制备及苯加氢性能的研究

利用浸渍还原法在Nafion117离子交换膜上制备银汞合金Nafion膜电极,考察了制备电极的主要因素,通过研究得到了浸渍还原法制备银汞合金Nafion膜电极的优化条件为:氯化汞浓度0.005mol/L,用浓度为0.1mol/LNa2S2O3络合,80℃下浸渍40min,用浓度1%(wt)的SnCl2做还原剂,还原时间2h,所制备的电极电阻较小,银汞结合比较致密,主要分布在膜的内表面.将制备的电极进行电化学性能评价,研究表明银汞比为1:1的电极对苯加氢的催化活性最高,同时生成环己烷的电流效率较高为39.68%,电极具有较好的活性及选择性.     

锂离子电池用无溶剂干法电极的制备及其性能研究

采用无溶剂电极制备技术成功制备了锂离子电池用LiNi0.8Co0.1Mn0.1O2干法电极片,采用扫描电子显微镜(SEM)和X射线能谱仪(EDS)对干法电极片的形貌和元素分布进行了分析测试,通过倍率充放电、交流阻抗、循环充放电等测试手段研究了干法电极片的电化学性能.结果表明:纤维状PTFE广泛地分布在LiNi0.8Co...     

半导体-电解液光电极体系研究 Ⅴ.聚苯胺膜对半导体光阳极的保护作用

聚苯胺(Polyaniline,简称PA)同聚吡咯一样,可以用电化学阳极氧化的方法由苯胺单体在导电基底上聚合成膜。Noufi等报道了把这种PA膜用于单晶Si等半导体光电极的保护。苯胺的电聚合可在水溶液中进行,操作比较方便。我们在聚吡咯工作的基础上,探讨了在单晶n-Si和n-GaAs电极上PA膜的电氧化生成,并考查了PA膜对这两种电极在不同电解质溶     

Fabrication of n-Cu2O electrodes with higher energy conversion efficiency in a photoelectrochemical cell

We observed an n-type photoresponse in cuprous oxide films, which were prepared by a simple method of immersing copper plates in a HCl solution of 3 pH at 40°C temperature, when they were used in a PEC cell. This photoresponse was much higher than the previously published values for n-Cu₂O electrodes which were prepared by other methods. The photocurrent obtained was in the order of 0.3 mA/cm² when the cell was illuminated with light intensity of 50 mW/cm². (The semiconductor electrode was biased to get a zero dark current.) The power conversion efficiency of the cell was 0.01%. The maximum quantum efficiency obtained was 15%. It is hoped that these values could be improved with a better understanding of the photoelectrochemical properties of the cell.     

Electrochemical oxidation of hydrazine and its derivatives on the surface of metal electrodes in alkaline media

Electrochemical oxidation of hydrazine and its derivatives on the surface of various metal electrodes in alkaline media was investigated. A comparison of various polycrystalline metal electrodes (Ni, Co, Fe, Cu, Ag, Au, and Pt) showed that Co and Ni electrodes have a lower onset potential for hydrazine oxidation than the Pt electrode. The onset oxidation potential of APA (aminopolyacrylamide), a hydrazine derivative (−0.127 V vs. reversible hydrogen electrode, RHE), was similar to that of hydrazine hydrate (−0.178 V vs. RHE) in the case of the Co electrode. APA oxidation was possible because of hydrazine desorption that was caused by APA hydrolysis. The hydrolysis reaction was brought about by a heat treatment. This result suggests that the hydrazine hydrolysis reaction of hydrazine derivatives makes it possible to store hydrazine hydrate safely.     

3D hierarchical nanostructured Ni–Co alloy electrodes on porous nickel for hydrogen evolution reaction

Nanostructured Ni–Co alloys decorated on 3D porous nickel electrodes for hydrogen evolution reaction (HER) are successfully prepared through a facile and effective electrodeposition method. By adjusting the current density of electrodeposition, Ni–Co alloys with different surface morphologies like nanocones, leaf-like structures and flakes can be obtained. The HER catalytic activity has been greatly reinforced with decorated Ni–Co alloys. Meanwhile, the HER performance of nanocone Ni–Co alloys outperforms that of leaf-like and flaky Ni–Co alloys. The nanocone Ni–Co alloys exhibit outstanding HER activity, only requiring an overpotential of 86.7 mV at 10 mA cm⁻², along with a low Tafel slope of 69.8 mV dec⁻¹ and 3.4 Ω charge transfer resistance. This nanocone electrode remains stable for 10 h of chronopotentiometric measurement. Such enhanced catalytic performance stems from the porosity and the high population of sharp edges, as well as surface oxidation/metallic states and synergistic effects between Ni and Co.     

Flame-assisted pyrolysis formation of Cu2O/Cu/TiO2 nanotube arrays to boost superior photo-electrochemical response

Herein, a flame-assisted pyrolysis technique is developed for one-step in-situ construction of Cu₂O/Cu/TiO₂ nanotube arrays. The structure and morphology of the obtained samples are systematically characterized. Interestingly, UV–vis absorption spectroscopy reveals that the introduction of Cu₂O and Cu considerably enhance light response of TiO₂ nanotube arrays in the visible region. Moreover, the composited electrode shows enhanced photo-electrochemical activity. Compared with blank TiO₂ nanotube arrays, not only the photocurrent and photo-voltage of composited electrodes are improved but also the stability is also enhanced. And, the maximum photo-conversion efficiency for composited electrode presents 4.71 folds larger than that of blank TiO₂ electrode. This enhancement is due to the faster charge separation/transportation ability of Cu and visible light response of Cu₂O. This research develops a novel and facile method for the in-situ fabrication of Cu₂O/Cu/TiO₂ nanotube arrays and demonstrates their improved utilization of solar energy.     

Effect of operating parameters on hydrogen production by electrolysis of water

This paper presents an experimental study of hydrogen production by alkaline water electrolysis using Zinc alloys as materials for cathode. The aim of this study is to select the best alloy for producing hydrogen on testing the effect of some operating parameters. Experiments were conducted on a water electrolysis cell with two electrodes (anode/cathode). Throughout these experiments, we have chosen to use NaOH solution with different concentrations as an electrolyte. Binary alloys: Zn95%Fe5%, Zn90%Fe10%, Zn85%Fe15%, Zn95%Cu5%, Zn90%Cu10%, Zn85%Cu15%, Zn95%Co5%, Zn90%Co10%, Zn95%Cr5% and Zn90%Cr10% (mass %) were prepared as electrodes for the cathode. The effect of electrode composition, the electrolyte concentration, the voltage and amperage applied on volume of hydrogen produced are experimentally investigated. The results showed that the performance of alkaline water electrolysis is significantly affected by these various factors. Indeed, this preliminary study revealed that cathodes elaborated by (Zn95%Cr5%) and (Zn90%Cr10%) (mass %) produce more hydrogen gas than other alloys, in a minimum durations over the range of operating parameters tested.     

Fabrication of reducing atmosphere electrodes (fuel electrodes) by electroless plating of copper on BaZr0.9−xCexY0.1O3−δ – A proton-conducting ceramic

Copper appears to be an interesting fuel electrode material for proton-conducting ceramic electrolytes (such as BaZr_0.9?xCe_xY_0.1O_3?δ) because it is stable at high temperatures in reducing and hydrocarbon-containing atmospheres. However, when deposited using organometallic Cu pastes/inks, these electrodes suffer from poor performance due to delamination issues and coating thickness (10–20 μm). Alternatively, electroless plating (ELP) is a method of depositing metal films – without utilizing electric power – that can achieve much thinner coatings than with pastes. In this work ELP of Cu was shown to be an alternative to Cu pastes for electrode fabrication on the non-electrically conductive, proton-conducting ceramic BaZr_0.8Ce_0.1Y_0.1O_3?δ. Pd, Ru, and Cu were investigated as activation catalysts, on which Cu was then plated. All three were found to produce thin electrodes (～1 μm) with good electrode/electrolyte adhesion. Scanning electron microscopy coupled with energy dispersive x-ray spectroscopy, x-ray fluorescence and x-ray diffraction were used to characterize the Cu-based ELP electrodes. Additionally, the ELP process was shown to be transferable to tubular substrates without significant modification to the procedure.     

Influence of order in stepwise electroless deposition on anode properties of thick-film electrodes consisting of Si particles coated with Ni and Cu

Nickel and copper were coated on Si particles by a stepwise electroless deposition technique in which the coating orders of the metals were exchanged. Thick-film electrodes for Li-ion batteries were prepared by a gas-deposition method using the coated Si particles, and the anode performance of these electrodes was investigated. For (Cu, Ni)-coated Si particles obtained by primary Cu deposition and successive Ni deposition, Cu and Ni metal layers were individually deposited on the Si particles. In contrast, in case of (Ni, Cu)-coated Si particles prepared by primary Ni deposition, Cu layer stacked on Ni layer owing to a high catalytic activity of Ni, forming a thicker coated layer. The latter electrode exhibited notably improved performance with the discharge capacities over 1000 mAh g⁻¹ maintained until 400th cycle. The layer stack of Cu on Ni is probably effective for a release of a stress from the Si particles during charge-discharge reactions.     

Formulation and characterization of ultra-thick electrodes for high energy lithium-ion batteries employing tailored metal foams

Increasing the thickness of a battery electrode without comprising cell electrochemical performance, such as power density and cycling stability, is very challenging. In this work, we demonstrate the utility of 3D (three dimensional) Cu foam framework as a current collector for building carbon negative electrodes as thick as 1.2 mm. When tested in a bipolar configuration, electrodes of 1.2 and 0.6 mm thick delivered capacities of over 350 mAh g⁻¹ (>95% of theoretical capacity) up to a C/5 rate. We have also assembled a full cell composed of a 1.2 mm thick negative electrode with Cu foam as the current collector and a 1.2 mm thick L333 (LiNi_1/3Mn_1/3Co_1/3O₂) positive electrode with Al foam as the current collector. The cell exhibited good capacity retention at low rates. These results underscore the promise of 3D foam structures in terms of enabling ultra-thick electrodes for high energy density battery applications.     

Ultra low Pt-loading electrode prepared by displacement of electrodeposited Cu particles on a porous carbon electrode

Ultra low Pt-loading and high Pt utilization electrodes were prepared by displacement of electrodeposited Cu on a porous carbon electrode. Copper particles were electrodeposited on a porous carbon electrode (PCE) by four-step deposition (FSD) at first. The size and dispersion of deposited Cu particles were markedly improved with application of the FSD. The Cu deposits were then displaced by platinum as dipping a Cu/PCE in a platinum salt solution. Sequentially, Pt particles supported on the PCE were obtained. The Pt/PCE electrode prepared via the FSD of Cu overcomes the problem of the hydrogen evolution reaction accompanied with direct platinum electrochemical deposition, and has a high Pt dispersion. The single cell consisting of the electrodes Pt/PCE via the FSD of Cu outputs a power of 0.45 W cm⁻² with ultra low Pt loadings of 0.196 mg cm⁻² MEA (0.098 mg cm⁻² per each side of the MEA) at no backpressure of reactant gases.