共查询到20条相似文献,搜索用时 109 毫秒
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旋转圆盘电极(RDE)体系主要用于低溶解度反应物的电极过程动力学研究. 在利用RDE技术研究不可逆电极反应动力学时,人们常利用Koutecky-Levich方程排除传质的影响,从总电流估算反应的动力学电流. 由于K-L方程是建立在系统满足稳态扩散模型的基础上,实际运用时如果体系偏离稳态扩散,就有可能对估算的动力学参数造成很大误差. 本文以氧气在多晶铂电极上的还原反应为例系统地估算了不同氧气浓度与电极转速下的误差,结果表明低氧气浓度与低圆盘转速的情况不满足稳态扩散条件,若此时仍根据K-L方程利用外推法进行分析,误差可达30%. 因此作者建议,在RDE体系中利用K-L方程估算动力学参数时,最好忽略低浓度与低转速下的数据,直接使用较高浓度与较高转速下的数据进行计算与分析. 相似文献
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利用逐步合成的方法,合成了一系列不同量硝酸处理的PtCo/C催化剂.通过燃料电池测试装置对催化剂进行了测试,结果表明PtCo/C催化剂在较低载量情况下,有着很好的性能:在50 kPa背压下,0.9 V下的电流密度达到44 mA·cm-2,0.8 V下的电流密度超过300 mA·cm-2;200 kPa背压下,最高功率密... 相似文献
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Clark等[1]研究苯阳极氧化过程,认为二氧化铅是最合适的电极,苯是二级反应,苯在阳极上首先氧化为产物对苯二醌,产物可进一步氧化成马来酸,直至氧化成二氧化碳.但Ito[2]等研究表明苯阳极氧化还有一个并行反应:苯直接氧化为马来酸.Fleszar和P... 相似文献
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利用旋转圆盘电极体系系统研究了不同pH下氧气在多晶Au电极上的还原反应,并计算了不同pH条件及不同超电势范围内的Tafel斜率.研究发现,同在酸性(但是pH不同)或同在碱性(但是pH不同)的介质中氧还原起始电位以及纯粹动力学控制区(电流较小的区域)的氧还原电流几乎不随溶液的pH值而变化.酸性条件下以及碱性条件的高超电势范围内,Tafel斜率接近120mV/dec;而碱性条件的低超电势范围内,Tafel斜率接近60mV/dec.金电极上ORR的活化超电势随着pH值的增加而降低约79mV/pH.初步讨论了pH对氧还原机理和动力学的影响及其内在原因. 相似文献
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质子交换膜燃料电池是一种能够将燃料的化学能直接高效地和环境友好地转化为电能的绿色能源技术。质子交换膜燃料电池具有能量转化效率高、启动快速、零排放或者低排放等优点,被认为是后石油时代最为重要的能源替代技术之一。然而目前使用的电催化剂存在铂用量高和稳定性不足等问题。开发高性能低Pt催化剂对于降低质子交换膜燃料电池成本、促进质子交换膜燃料电池的大规模商业化应用具有十分重要的意义。Pt基金属间化合物是一类具有严格元素化学计量比和规整原子排列结构的合金化合物,其氧还原反应催化活性明显优于相应的Pt基无序合金及纯Pt催化剂,被认为是最具应用前景的低Pt催化剂之一。本文着重从催化机理、制备技术、组成调控、颗粒度调控、形貌调控和晶体结构等几个方面介绍了Pt基金属间化合物催化剂近来的研究进展,以及这类催化剂在质子交换膜燃料电池阴极氧还原反应中的应用研究情况,指出了这类催化剂目前尚存在的不足及挑战,并展望了未来的研究发展思路及方向。 相似文献
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Guo SX Zhao SF Bond AM Zhang J 《Langmuir : the ACS journal of surfaces and colloids》2012,28(11):5275-5285
Graphene modified electrodes have been fabricated by electrodeposition from an aqueous graphene oxide solution onto conducting Pt, Au, glassy carbon, and indium tin dioxide substrates. Detailed investigations of the electrochemistry of the [Ru(NH(3))(6)](3+/2+) and [Fe(CN)(6)](3-/4-) and hydroquinone and uric acid oxidation processes have been undertaken at glassy carbon and graphene modified glassy carbon electrodes using transient cyclic voltammetry at a stationary electrode and near steady-state voltammetry at a rotating disk electrode. Comparisons of the data with simulation suggest that the transient voltammetric characteristics at graphene modified electrodes contain a significant contribution from thin layer and surface confined processes. Consequently, interpretations based solely on mass transport by semi-infinite linear diffusion may result in incorrect conclusions on the activity of the graphene modified electrode. In contrast, steady-state voltammetry at a rotating disk electrode affords a much simpler method for the evaluation of the performance of graphene modified electrode since the relative importance of the thin layer and surface confined processes are substantially diminished and mass transport is dominated by convection. Application of the rotated electrode approach with carbon nanotube modified electrodes also should lead to simplification of data analysis in this environment. 相似文献
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The effect of surfactants on surface instabilities of thin liquid film flow on a rotating disk was studied at different flow rates Q (0.5相似文献
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A liquid membrane disk electrode, LMDE, and a liquid membrane ring-liquid membrane disk electrode, LMRE-LMDE, were developed by placing a gelled polyvinyl chloride thin membrane impregnated with 2-nitrophenyl octyl ether, NPOE-LM, on the surface of a glassy carbon, GC, disk or ring electrode. The voltammogram for the ion transfer at the interface between an aqueous solution, W, and NPOE-LM was recorded by setting the developed electrode in W and rotating at a rate, omega, between 0 and 4000 rpm. The sensitivity of the ion-transfer current at the WINPOE-LM interface, I, was enhanced to be more than 100 times better than that at the WINPOE (solution) interface when LMDE was rotated at omega higher than 200 rpm. The reversibility of the ion transfer reaction could be evaluated based on the dependence of I on omega of LMDE, and the reaction product at LMDE could be identified at LMRE when the rotating LMRE-LMDE system was adopted. 相似文献
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Conductive polymer (poly-o-phenylenediamine and poly-3-methylthiophene) films were synthesized on a rotating disk electrode. Dependences of the limiting penetration currents on the nature of the polymer and film thickness were obtained in solutions containing electroactive substances (hydroquinone, quinone) reducing or oxidiring at redox potentials beyond the range of polymer electroactivity (selected by adjusting the pH value). The transport of hydroquinone and quinone test species through the pores in polymer films was examined based on the results of these studies, and the degree of film porosity was evaluated. 相似文献
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In the present work, the applicability of thin mercury film on a rotating disk electrode (TMF-RDE), to assess the free metal ion concentration by the absence of gradients and Nernstian equilibrium stripping (AGNES), is evaluated. The thickness of the mercury film and several AGNES parameters has been optimized. A nominal 16 nm film is chosen due to the higher signal (faradaic current) relative to the value of the noise (capacitive current). Due to the smaller volume to area ratio, the deposition time needed to reach a certain preconcentration factor (Y) is much shorter than in larger electrodes, like the HMDE. The limit of detection (3σ) for lead(II) is 7.4 × 10−9 M and 7.2 × 10−8 M for a Y of 5000 (deposition time of 150 s) and 1000 (deposition time of 100 s), respectively. A specific mathematical treatment is developed in order to subtract a corrected blank taking into account the degradation of the thin film (presumably, falling down of drops). The couple TMF-RDE/AGNES is successfully applied for speciation purposes in the systems Pb(II)-latex nanospheres and Pb(II)-IDA (iminodiacetic acid), where the stability constants calculated for both systems agree with values reported in the literature. 相似文献
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Abdelmalek Zahra Khan Sami Ullah Waqas Hassan Al-Khaled Kamel Tlili Iskander 《Journal of Thermal Analysis and Calorimetry》2021,144(5):1639-1654
Journal of Thermal Analysis and Calorimetry - The revolution in nanotechnology has made new developments toward enhancement of energy resources which play a substantial role in the growth of... 相似文献
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Corrosion of iron in slightly acidified sodium sulphate solutions (mainly pH 4.5) in the open air was studied with a rotating disk electrode method at room temperature.Microscopic observations of corroded iron disk surfaces in the pH 4.5 solution revealed that iron initially corrodes locally with the formation of round pits of 10–30 μm in diameter and of(0.6–1.3) × 103 in number per apparent square centimetre followed by the U-shaped brown protective wall formation of precipitates (rust) outside the pits. Each protective wall is formed along the lines of flow of the solution adjacent to the iron surface and each pit is located near the upstream end of the wall. Steady state of corrosion sets in when the parts of surface area surrounded by the wall are completely covered with a microscopically non-porous rust film.The amount of iron in the rust film and the total amount of corrosion of iron including that in the film increase parabolically with the increase in the time of immersion. The amount of iron in the film increases in proportion to the total amount of corrosion independently of the speed of rotation of the disk electrode even in the steady state.The fraction of area of iron surface not covered with the film decreases with time and reaches a certain fixed value in the steady state: the value is smaller at higher rotational speed. The corrosion rate is proportional to the uncovered area, as the corrosion is near the steady state. The pH of the bulk solution increases as corrosion progresses.The corrosion rate of iron can be well interpreted by assuming that the rate is controlled by the diffusion of oxygen from the bulk solution to the surface of iron and that the rust film on iron impedes the diffusion of oxygen. 相似文献
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This paper describes the use of an aluminum electrode plated by metallic palladium and modified by Prussian blue (PB/Pd-Al)
in the electrocatalytic reduction of hydrogen peroxide (H2O2). The effect of pH on the electroreduction of H2O2 on the modified electrode is investigated and a simple irreversible reduction pathway is suggested. The electroreduction
kinetics including transfer coefficient α, potential-dependent charge transfer rate constants k
f, and diffusion coefficient D are estimated by means of forced hydrodynamic voltammetry using a rotating disk PB/Pd-Al electrode. The mean values obtained
for kinetics are 0.38, 10−2 cm−1, and 7.6 × 10−6 cm2 s−1, respectively. The long-term stability of the modifying layers on the Al substrate was studied. 相似文献