直接甲醇燃料电池性能研究

研究了聚合物电解质膜直接甲醇燃料电池性能。 2 0 %Pt -10 %Ru/C和 2 0 %Pt/C分别作为甲醇氧化和氧还原催化剂。通过改变甲醇阳极催化层中Nafion与PTFE的含量研究了电池的电流 -电压特性。结果表明 ,催化层中Nafion含量的影响对电池性能至关重要 ,而PTFE的影响则较小。研究得出催化层中Nafion的最佳含量为 7%。通过在电极表面刷一层Nafion溶液 ,明显提高了电池性能。在低Pt载量条件下 ,即阳极Pt含量 0 .6mg/cm2 ,阴极Pt含量 1.1mg/cm2 ,阴极空气近大气压条件下 ,t =60℃ ,甲醇浓度 1mol/L时 ,单电池开路电压为 0 .6V左右 ,0 .4V时电流密度为 3 0mA/cm2 ,0 .2V时电流密度为 10 6mA/cm2 。甲醇阳极催化层表面的扫描电镜 (SEM )观察表明催化层中Nafion含量不同 ,电极结构不同。     

膜电极性能的影响因素研究

文章以有机多孔膜为电极支撑体制备了亲水电极,用于质子交换膜燃料电池(PEMFC)。考察了电极在全氟代磺酸离聚物(Nafion)的玻璃化温度处理、催化层中Nafion的含量、以及不同厚度的有机多孔膜等因素对电极性能的影响。测试结果表明亲水电极中Nafion分子的有序排列可以减小电极的极化,减小作为电极支撑体的有机多孔膜的厚度有利于电极性能的提高。采用70%Pt/C制备电极时,Nafion的最佳含量为25%,在1000mA/cm2的电流密度下,电池电压为0.615V。     

Na~+对PEMFC Pt/C气体扩散电极的影响

采用燃料电池半电池体系模拟了质子交换膜燃料电池(PEMFC)中Na+污染气体扩散电极时的工况,研究了Na+对PEMFC常用的Pt/C气体扩散电极性能的影响.通过循环伏安曲线和电化学阻抗谱,测试了电极在Na+污染前后催化层电化学比表面积(ECA)和电极反应界面上的电荷转移电阻发生的变化.实验结果表明,随Na+污染浓度的增大,电极性能逐渐下降;污染后电极催化层电化学活性比表面积出现明显减少,当污染物浓度为10 000X 10-6时,ECA降低了43%;外加相同电位时,随Na+污染的增加,电极反应界面上的电荷转移电阻逐渐增大.Na+的存在对Pt/C气体扩散电极具有明显毒化作用.     

质子交换膜燃料电池的初步研究

组装了质子交换膜燃料电池 (PEMFC)单体并研究了其性能。由于氧电极的性能好坏是质子交换膜燃料电池放电性能好坏的关键 ,因此在电池氢电极侧用部分氢电极作为内氢参比电极 ,可以方便地作出氧电极的极化曲线并对其性能进行评价。考察了催化剂载体、膜电极组件 (MEA)的结构和运行条件对氧电极性能的影响并使用非线性最小二乘法拟合了电池参数。实验表明 :电池的最佳运行温度为 80℃ ,压力为氧气压力 0 .3MPa ,氢电极为 0 .3MPa ,催化层的PTFE最佳含量为 35 % ,Nafion含量为 1mg/cm2 ,Pt含量可以降至为 0 .5mg/cm2 。     

电极组分对质子交换膜燃料电池性能的影响

在疏水碳纸中加入聚四氟乙烯(PTFE)并增加其含量,实验表明,过多的PTFE的加入,降低了碳纸的电导率,阻塞了气体电极的孔隙,导致电池性能下降,20% PTFE的含量较为合适;在催化层中添加造孔剂,增大了空气中氧气和电极的接触面积,减小了扩散极化,提高了电池的性能,使电池在Pt载量为0.5 mg ·cm-2、常压氢气和空气的操作条件下,其功率密度达到了0.3 W·cm-2 。     

质子交换膜燃料电池膜电极组件研究

膜电极组件(MEA)是质子交换膜燃料电池的核心部件。系统地研究了MEA的组成和结构对其性能的影响。研究提出:催化层中掺杂Nafion聚合物的亲水电极比传统的催化层中掺杂PTFE的疏水电极性能有了较大的提高;不同种类质子交换膜对MEA的性能影响很大,Nafion112和Dow膜是目前比较适宜的质子交换膜;采用石墨类碳纸的电极性能高于采用碳纤维类碳纸的电极;电极催化层中Nafion聚合物的最佳含量比为30%左右。根据氢电极和氧电极反应难度的不同,提出为了减少催化剂的用量同时不显著影响电池的性能,氢电极的铂载量应该低于电极的观点,并通过了实验验证。     

质子交换膜燃料电池阴极数学模型

Ｓｔｅｆａｎ－Ｍａｘｗｅｌｌ方程用于氧在扩散层内传递;稳态连续方程和Ｆｉｃｋ 第一定律分别用于氧在催化层内气体通道和电解质膜中传递,采用一维宏观均匀模型,建立了质子交换膜燃料电池氧电极的数学模型。给出了反应速度和氧气浓度在催化层内分布,并分析了各种参数对氧电极性能的影响。结果表明：（１）当催化层内气相孔隙率为０．０１以上,则氧在催化层内浓度分布就趋于均匀;（２）催化层厚度为２５ μｍ 左右最佳,过厚影响传质,过薄不能提供足够的反应界面;（３）提高催化层内质子电导和催化剂的有效表面积将极大地提高电极性能;（４）低电流密度时,反应在催化层内分布均匀;高电流密度时,反应集中在催化层靠近扩散层一则。     

正交设计法确定PEMFC中催化层的最佳配比

利用正交实验设计法优选出质子交换膜燃料电池(PEMFC)电极催化层制备的最佳条件,即制备亲水电极。催化层中不含聚四氟乙烯(PTFE),当Nafion的含量为1.4mg·cm-2、Pt含量为0.4mg·cm-2,以常压的H2和空气分别作为燃料气和氧化剂,电池的最高功率可达到0.37W·cm-2。研究表明,提高Pt/C中的Pt含量将是提高催化剂性能的有效途径。     

M_cPt_s纳米催化剂的电催化氧还原性能

采用两步化学还原法合成不同Pt壳层厚度的M_cPt_s(M=Ni、Co、Cu和Ag)纳米粒子,用XRD、XPS和TEM测试分析粒子的结构和组成,动电位扫描法测试对氧还原反应的活性和抗甲醇性能。M_cPt_s纳米粒子为球形,平均粒径为35 nm,Pt壳层平均厚度约6 nm;相对于Pt/C,当M为Ni、Co时,氧还原活性提高,当M为Cu、Ag时,氧还原活性降低;Co、Cu和Ag为核芯,还可提高M_cPt_s/C的抗甲醇性能。     

SPE水电解池氧电极研究

氧电极是固体聚合物电解质(SPE)水电解池(WE)的控制电极,其中扩散层、催化剂的性能将直接影响电解池性能的高低。采用热分解、酸浸蚀、电沉积方法,对钛氧电极扩散层基体进行表面改性研究;探讨了氧电极催化剂对WE极化性能的影响;同时考察了温度、氧电极扩散层对WE性能的影响。结果表明:电沉积法处理钛氧电极扩散层可以使电阻降低,并且在大气中搁置电阻也不会增加;IrO2-RuO2氧电极复合催化剂具有最佳的催化活性;随着电解温度升高,电解电压下降;以电沉积法处理的钛网为氧电极扩散层时,WE性能得到明显提高,在常压、70℃条件下,电解电压为1.65V时,电流密度大于1A/cm2。     

质子交换膜燃料电池中氢电极和氧电极性能的研究

采用三种活性碳和三种还原剂,通过化学还原得到Pt/C催化剂.将涂在碳布上的Pt/C催化剂在125℃下热压在Nafion膜上,制成氢电极和氧电极,用循环伏安和极化方法研究了Pt/C-Nafion膜电极的性能.结果表明,这种电极的性能主要与活性碳的种类有关,而制备催化剂的还原剂起着次要的作用.对质子交换膜燃料电池的电流-电压性能和放电行为进行了初步研究.     

PTFE粘结的PEMFC氧电极性能研究

本文研究了PEMFC中氧电极催化剂层内PTFE含量和铂载量对电池性能的影响,并运用TEM和XRD分析了运行一段时间后电池性能衰减的原因。试验发现:1)PTFE含量为30w％时电池性能较好;2)铂载量增加,电池性能改善,但催化剂层过厚会引起传质问题。电池运行后性能略有衰减可能由两个因素引起:1)铂晶粒变大2)氧电极催化剂层防水特性发生变化。     

NiCr Alloy As Both Absorption Layer and Top Electrode onto Pb(Zr0.3Ti0.7)O3 Thin Films for Infrared Sensors

NiCr alloys prepared by dc magnetron sputtering are considered to apply simultaneously both the absorption layer and the top electrode on PZT thin films for infrared sensors. NiCr alloys deposited with dc powers of Ni 80 and Cr 50 W showed the most stable oxidation resistance even at 600°C in an oxygen ambient. They have a resistivity of approximately 70 μΩ-cm and a rms roughness of 2.0 nm in samples annealed at 600°C for 5 min in O₂. The NiCr/PZT/Pt capacitors showed a well-saturated hysteresis loop having a remanent polarization of 20 μC/cm². Ultra-thin NiCr alloys showed a possibility as a top electrode for infrared sensors.     

Platinum alloys and iridium bottom electrodes for perovskite based capacitors in dram applications

Abstract

Two types of potential bottom electrode structures for integration of ferroelectric materials in DRAM technology have been investigated: one based on iridium, the other based on platinum alloyed with oxygen gettering elements, such as B and Ti. The electrode structures, deposited on Si substrates, have been annealed in oxygen at 650°C for 30 min and characterized by RBS and AES. It was found that alloying the Pt with 3% of alloying elements had no beneficial effect and did not improve the properties of Pt as a barrier to oxygen diffusion. At the investigated annealing conditions, oxygen diffuses through Pt or its alloys and oxidizes the underlaying material. On the other hand, a thickness of 1100 Å of Ir was found to provide a barrier to oxygen diffusion under the same conditions. A layer of Ta in contact with Pt or Ir was found to deteriorate the barrier properties of both metals at the investigated annealing conditions.     

Platinum (100) Hillock Growth in Pt/Ti Electrode Stack for SrBi2Ta2O9 Ferroelectric Random Access Memory

The ferroelectric material SrBi₂Ta₂O₉ (SBT) has been extensively investigated in connection with integrating nonvolatile ferroelectric random-access memory (FeRAM). The SBT layer must be annealed in an oxygen atmosphere after deposition to crystallize the ferroelectric oxide film, which induces Pt hillock formation in a Pt/Ti electrode stack. The Pt hillock in a Pt/Ti electrode stack has been the main concern in SBT FeRAM due to reliability problems, such as capacitor shorts. Reportedly, the compressive stress generated in thin film is widely accepted as being responsible for the occurrence of hillocks in thin film and the main mass transport mechanism for hillock formation is the grain boundary diffusion for thin film with a columnar structure. In this study, three factors are considered in the total compressive stress generated during both deposition and post-annealing in Pt/Ti electrode stack: intrinsic stress, thermal stress, and extrinsic stress. Moreover, we found that an orientation relationship of Pt (100)_hillock//Pt (111)_{thin film} existed between the Pt hillock and the thin film. The Pt hillock was a single crystal, having facets with polyatomic steps. From these results, we suggest that the Pt hillock growth mechanism is the layer growth of flat faces, which shapes the hillock into a tetrahedron single crystal.     

PZT Capacitors on Top of CrTiN/TiN Double Barrier Layers

In this paper we investigated the thermal stability of a novel CrTiN/TiN double barrier, compared to those of TiN and CrTiN single layer barriers. The CrTiN/TiN double layer was stable against heat treatments at higher than 700°C in oxygen ambient for 30 min. However, the double layer showed a severe Pt and Cr interdiffusion issue after crystallization annealing for PZT. We found that pre-annealing treatments prior to deposition of Pt significantly reduced the interdiffusion. In addition, we also demonstrated ferroelectric characteristics of PZT capacitors on top of Pt/CrTiN/TiO₂/Si bottom electrode system for ultra-high density memory applications.     

Effect of time and polarization on kinetics of the oxygen electrode reaction at an Au∣YSZ interface

The oxygen electrode reaction at the interface gold∣yttria stabilized zirconia was investigate using microelectrodes by chronoamperometry and electrochemical impedance spectroscopy, with emphasis put on effect of prolonged polarization of the electrode. Two interesting phenomena were observed: (a) generally, the long-lasting negative polarization resulted in a slow monotonous decrease of the current flowing through the electrode, (b) the reaction mechanism was less complicated for the polarized then unpolarized electrodes, which resulted in a relatively simply equivalent circuit used for modelling the former ones. On the basis of the data obtained, the apparent exchange currents normalized vs. the three phase boundary length and Tafel slopes were determined. The methods of determining the three phase boundary length were discussed. The reconnaissance data obtained for the Pt microelectrode are also reported.     

Development of a new annealing process to allow new top electrode materials for SrBi2Ta2O9 capacitors

Abstract

Using the Rapid Thermal Annealing (RTA) process, a technique has been established to obtain SrBi₂Ta₂O₉ (SBT) films which showed well-shaped hysteresis curves without a postannealing process after top electrode deposition, maintaining high remanent polarization (Pr) values. RTA conditions were optimized for nucleation of SBT. The effect of a seed layer on the film properties became obvious. This process allowed top electrode materials other than Pt. High remanent polarization (Pr) values could be also obtained with Pd top electrodes.     

空气电极催化层中导电炭材料的研究(II)

将气相生长碳纤维(VGCF)加入到锌空气电池空气电极催化层中,通过热压成型制备三相气体扩散电极。用电流-电位极化曲线研究了这种空气电极的性能及VGCF加入量对电极性能的影响。结果表明,添加一定量的VGCF,可以降低电极极化,提高空气电极性能。     

钙钛矿型催化剂LaNi_(0.8)Co_(0.2)O_3性能的改进

通过改进的溶胶-凝胶法制备了钙钛矿型氧化物LaNi0.8Co0.2O3,研究了煅烧温度对催化剂的影响.采用XRD、SEM对催化剂的结构和表面形貌进行了分析;用极化曲线、恒流放电曲线研究了催化剂在7 mol/L KOH中的电化学性能.采用改进的溶胶-凝胶法,在500 ℃下煅烧制得的催化剂团聚最小,且电化学性能最好.当电极电位为-0.4 V(vs. Hg/HgO)时,氧还原的电流密度为230 mA/cm2.