Pt/纳米碳管空气电极氧还原反应的电催化性能

以不同质量比的铂、纳米碳管、活性炭为催化层制备空气电极并测定其稳态极化曲线和交流阻抗.研究发现,纳米碳管经硝酸处理后其氧还原反应性能得到提高,特别是将表面氧化后再沉积Pt,对氧的电还原反应影响更显著.以质量比4∶1的活性炭/纳米碳管载Pt制备的空气电极,在过电位ηc为500～600mV下,氧还原电流可达600～700mA·cm-2.EIS测试表明,纳米碳管载Pt后的欧姆极化阻抗和电化学阻抗均非常小.     

纳米碳管空气电极在氧还原反应中的电催化性能

电化学阻抗谱;纳米碳管空气电极在氧还原反应中的电催化性能     

硬碳材料电极首周嵌钠过程的电化学阻抗谱研究

运用电化学阻抗谱（EIS）研究了硬碳材料电极嵌钠的过程,发现EIS谱由两个半圆和一条斜线组成,两个半圆可归因于接触阻抗和钠离子通过固体电解质界面膜（SEI膜）扩散的过程和电荷传递的过程,斜线域则反映了钠离子在硬碳材料颗粒内部的固态扩散相关的斜线.通过选取适当的等效电路,对实验结果进行拟合,可以得出硬碳电极首周嵌钠过程中SEI膜电阻、电子电阻等随电极极化电位的变化规律.     

乙烷质子传导膜燃料电池的极化与反应机理

制备了以乙烷作为燃料电池膜电极组装(MEA)及构建了单电池系统。研究了Nafion材料作为质子传导膜、Pt/C作为电极催化剂构成的燃料电池在105 ℃和0.4 MPa电化学性能。采用交流阻抗分析法、色谱分析法及根据Faraday定律,考察了电池的电极极化过程,确定了电池的反应产物并探讨了电极的电化学反应机理。研究结果表明,乙烷燃料电池内阻引起的欧姆极化很小,电池阴极的极化主要是欧姆极化过程所控制,阳极极化主要为活化和浓差过程控制,阳极极化比阴极极化显著,乙烷燃料电池的极化主要在阳极侧;在实验操作条件下,阴极反应产物为水,阳极反应的主产物为CO₂且含有少量的CO,电池反应产物不含乙烯。     

金属酞菁类大环化合物对氧气还原反应催化行为的阻抗谱研究

通过电化学交流阻抗法研究了3种金属酞菁类大环化合物(FePc, CoPc, FeCoPc2)在碱性溶液中对氧气还原反应(ORR)的电化学催化行为, 各电极的交流阻抗 Nyquist 图谱在高频区和低频区均呈现出2个较明显的半圆和半圆之间(中频区)的压扁的弧形, 采用Zsimpwin阻抗谱分析软件对-02 V(vs. Hg/HgO)电位下的各交流阻抗谱进行等效电路拟合, 提出空气电极ORR反应的等效电路, 并对等效电路中各动力学参数进行了解释, 通过分析得出金属酞菁在碱性溶液中对ORR催化反应是一个伴随中间产物HO-2的2电子转移过程. 同时, 等效电路的拟合结果表明, FeCoPc2/C作为ORR催化剂对减小Rc+Rct效果比FePc/C和CoPc/C明显, 具有更高的催化活性.     

新型CNT/nano-TiO_2复合膜电极的制备及其异相电催化性能

采用溶胶-凝胶法制备了碳纳米管/纳米TiO2(CNT/nano-TiO2)复合溶胶,通过提拉法将复合溶胶涂覆在Ti基体上制得CNT/nano-TiO2复合膜修饰电极(C电极),其电化学性能经循环伏安、计时库仑、交流阻抗谱(EIS)等方法研究.研究结果表明,CNT可阻碍nano-TiO2粒子团聚.在循环伏安图中,C电极的氧化还原峰电流比nano-TiO2膜修饰电极(P 电极)的高出两倍多.通过对草酸溶液的异相电催化反应进一步证明C电极比P电极具有更高的电催化活性,而且对双氧水也有很强的异相电催化还原能力.     

La1－xSrxNi1－yCoyO3双功能氧电极的电化学性能

采用溶胶-凝胶法制备了一系列La1－xSrxNi1－yCoyO3（x=0、0.1、0.2、0.5； y=0～1.0）型的钙钛矿催化剂，并以活性碳为载体制备双功能氧电极.对催化剂进行了XRD结构分析以及XPS表面分析.采用三电极体系测试了氧电极的稳态极化曲线和电化学交流阻抗谱并对其阴极极化和阳极极化谱图进行了分析.实验表明，对于LaNiO3化合物，B位掺杂可显著提高催化剂表面的B离子浓度, 从而提高电催化性能；而A位掺杂由于导致有序化氧空位的增多和电导的降低而造成活性下降.电极氧还原反应的极化主要由电荷转移反应和能斯特扩散过程造成.     

Pd/Mm(富铈稀土)薄膜电极在KOH溶液中的电化学行为

利用磁控溅射法制备了Pd/Mm(Mischmetal)混合稀土薄膜,采用X射线衍射、AFM及循环伏安和交流阻抗谱等电化学测试技术研究了Pd/Mm稀土薄膜的晶体结构、表面形貌及其在KOH溶液中的电化学行为.结果表明,Pd/Mm薄膜表面的Pd层由纳米级的孤岛状颗粒构成,颗粒大小为100～200 nm.循环伏安法研究表明,氢的电化学氧化和还原均通过表面Pd金属层进行.Pd/Mm稀土薄膜电极的交流阻抗图由两个容抗弧组成,低频区的容抗弧对应氢在电极中的固态扩散过程,而高频段的容抗弧对应氢在电极表面的电化学还原过程,其中氢在薄膜电极内部的扩散是速率控制步骤.     

贮氢电极的电化学研究（Ⅱ）—贮氢电极的交流阻抗研究

用交流阻抗的方法对贮氢电极进行了研究。实验表明，贮氢电极的交流阻抗图由两个半圆组成，高频区半圆对应于电化学反应，低频区半圆对应于氢原子在贮氢合金表面的吸附过程。低频区的半圆受电极活化次数和放电深度的影响。活化次数越多、放电时间越长、低频区半圆越小。提出了贮氢电极的等效电路图，对这些实验结果作出了解释。     

功能高分子膜离子选择电极研究 Ⅵ.压片PVC膜氯离子选择电极的暂态极化行为

在零电流条件下测量离子选择电极的电位分析已成为一种重要的电分析化学方法.Buck等首先用交流阻抗法研究了玻璃膜、晶态膜、液膜及PVC膜等一些电极的交流阻抗行为,Cammann和Rechnitz等用恒电位和恒电流阶跃法研究了缬氨霉素钾电极的极化行为,Powley等用双脉冲方法测定了Ca~(++)、F~-等电极的电导行为,并根据脉冲电流和溶液离子浓度的关系提出了离子选择电极的双极性脉冲电导分析法.到目前为止,还未见有功能高分子膜离子选择电极电化学极化行为研究的报道. 本文用快速三角波电位法和快速方波电位法研究了功能高分子压片PVC膜氯离子选择电极的暂态极化行为,计算了膜电极的一些电化学参数,讨论了影响膜电化学性质的因素.     

纳米碳管作为氧扩散电极催化层第二相碳载体的电极特性

A novel gas diffusion electrode using binary carbon supports (carbon nanotubes and active carbon) as the catalyst layer was prepared. The electrochemical properties for oxygen reduction reaction (ORR) in alkaline electrolyte were investigated by polarization curves and electrochemical impedance spectroscopy. The results show that the binary-support electrode exhibits higher electrocatalytic activity than the single-support electrode, and the best performance is obtained when the mass ratio of carbon nanotubes and activated carbon is 50 ∶50. The results from their electrode kinetic parameters indicate that the introduction of carbon nanotubes as a secondary support provides high accessible surface area, good electronic conductivity and fast ORR kinetics. The electrocatalytic activity of binary-support electrodes is obviously improved by the deposition of Pt nanoparticles on carbon nanotubes, even at very low Pt loading (45.7 μg/cm2). In addition, the EIS analysis results show that the process of ORR may be controlled by diffusion of oxygen in the thin film for binary-support electrodes with or without Pt catalyst.     

Carbon nanotubes as a secondary support of a catalyst layer in a gas diffusion electrode for metal air batteries

In this paper, we report the use of binary carbon supports (carbon nanotubes (CNTs) and active carbon) as a catalyst layer for fabricating gas diffusion electrodes. The electrocatalytic properties for the oxygen reduction reaction (ORR) were evaluated by polarization curves and electrochemical impedance spectroscopy (EIS) in an alkaline electrolyte. The binary-support electrode exhibits better performance than the single-support electrode, and the best performance is obtained when the mass ratio of carbon nanotubes and active carbon is 50:50. The results from the electrode kinetic parameters indicate that the introduction of carbon nanotubes as a secondary support provides high accessible surface area, good electronic conductivity, and fast ORR kinetics. Furthermore, the effect of CNT support on the electrocatalytic properties of Pt nanoparticles for binary-support electrodes was also investigated by different loading-reduction methods. The electrocatalytic activity of the binary-support electrodes is improved dramatically by Pt loading on CNT carbon support, even at very low Pt loading. Additionally, the EIS analysis results indicate that the process of ORR may be controlled by diffusion of oxygen in the electrode thin film for binary-support electrodes with or without Pt catalyst.     

钒液流电池用石墨毡电极电化学活化机理的交流阻抗研究

研究了不同氧化程度下的石墨毡在钒溶液中的吸附性、润湿性及其交流阻抗图谱(EIS), 结果发现随着氧化程度增加, 吸附性和润湿性增强; 交流阻抗谱包括两个半圆和一条直线, 高频半圆对应离子的吸脱附反应, 低频半圆对应电化学反应, 直线对应离子在溶液中的扩散过程. 随石墨毡氧化程度的增加, 低频半圆显著减小, 通过等效电路拟合及动力学参数计算, 发现电荷传递电阻显著减小.     

La0.8Sr0.2MnO3／YSZ高温电极交流阻抗研究

用交流阻抗方法研究了Ｌａ０．８Ｓｒ０．２ＭｎＯ３电极上进行的氧化电化学还原反应。实验表明反应速度控制步骤随反应温度，氧分压及过电位发生显著变化，近平衡下反应的ｒｄｓ为氧的解离吸附过程。强阳极极化下，电解质表面产生大量电子空穴；强阴极极化下，ＬＳＭ电极表面形成大量氧空位，二者的结果均使界面电导增加，电化学反应区扩展。     

Preparation and layer-by-layer self-assembly of positively charged multiwall carbon nanotubes

The report described a method of more stably dispersing oxidized carbon nanotubes (CNTs) by forming complex with polycation and the layer-by-layer self-assembly behavior of the complex with polyanion was studied. The properties of the self-assembled multilayer film containing carbon nanotubes were studied. Cyclic voltammetry, UV-vis-NIR spectroscopy, electrochemical impedance spectroscopy and scanning electron microscopy were used for characterization of film assembly. UV-vis-NIR spectroscopy and cyclic voltammetry study indicated the uniform growth of the film. Electrochemical impedance spectroscopy results showed that incorporating of carbon nanotubes in the polyelectrolyte multilayers decreased in the electron-transfer resistance R_ct, indicating more favorable electrochemical reaction interface. The electrocatalytic property of the multilayer modified electrode to NADH was investigated mainly with different numbers of the bilayers and the results showed that along with the increase of the assembled bilayers the overpotential of NADH oxidation decreased. The detection limit could reach 6 μM at a detection potential of 0.4 V.     

Electrochemical Determination of Dopamine Using a Carboxyl-functionalized Carbon Nanotube-Modified Carbon Paste Electrode Doped with Polymeric Ferric Sulfate

A novel electrochemical device for the sensitive determination of dopamine was developed based on a carbon paste electrode with polymeric ferric sulfate doped in the carbon paste and a carboxyl-functionalized carbon nanotube thin film on the surface. The modified electrode was characterized by scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The conditions for the preparation of electrode were optimized. The carbon nanotubes were shown to be stable on the surface of carbon paste electrode. The novel electrochemical device provided excellent activity toward dopamine. Amperometry and differential pulse voltammetry were used for the determination of dopamine in pH 7.0 phosphate buffer with a long linear range from 0.8 to 261?µM and a detection limit of 0.2?µM. The modified electrode showed excellent repeatability, good stability, and satisfactory reproducibility, thus demonstrating potential for practical applications.     

含氮磷酸锂薄膜在空气中的稳定性

利用射频(RF)磁控溅射方法制备了含氮磷酸锂(LiPON)薄膜. 采用SEM、XRD、XPS等技术以及交流阻抗法和电位线性扫描法, 研究了空气湿度对LiPON薄膜形貌、组成和性能的影响. 结果表明, LiPON薄膜在湿度为40%的空气环境中放置24 h后, 将发生明显的水解反应, 使LiPON薄膜表面形貌变得疏松、局部突起; PH3和NH3的产生, 使薄膜中磷元素和氮元素含量减少, 而Li2CO3的生成, 则使薄膜中碳元素和氧元素含量有明显的增加. LiPON电解质薄膜形貌和组成的变化, 造成了薄膜电化学性能的严重恶化.     

定向多壁碳纳米管电化学储氢研究

利用恒流充放电、循环伏安曲线(CV)和电化学阻抗技术(EIS)等方法对定向多壁碳纳米管(AMWCNTs)储氢的电化学行为及其储氢机制进行了探讨.研究表明,定向AMWCNTs-Cu电极有较高的电化学储氢性能,其储氢容量在1500mA/g的电流密度下可以达到1162mA·h/g.定向AMWCNTs的电化学储氢能力强与其空间结构有关,而铜粉的加入有利于提高碳纳米管的电催化反应表面积和电极电化学反应活性,有利于氢在碳纳米管中扩散,从而提高了碳纳米管电极材料的储氢量.