【作者】 马敏；

【导师】 蔡文斌； 柳厚田；

【作者基本信息】 复旦大学 ， 物理化学， 2007， 博士

【摘要】 表面电化学是表面科学与电化学的重要交叉学科。目前表面电化学的热点之一是生物界面电化学。其研究内容主要包括构建、表征和使用通过生物分子或相关分子构建的具有生物活性的界面。这种电极／电解液功能界面不仅能为生物分子的电子传递等研究提供模型场所，还对电催化和生物传感的研究提供潜在信息。金属卟啉广泛存在于自然界，是生物体内各种蛋白质的重要辅基。铁原卟啉（简称FePP）是一种重要的金属卟啉，是血红蛋白、肌红蛋白、细胞色素c和过氧化酶等蛋白（heme-proteins）共同的活性组分，在生物体内具有运输和催化等重要生理功能。近年来，又发现它与一氧化氮的结合（亚硝酰化）和血管舒张、神经传导和细胞毒化等生理过程密切相关。另外它还对不少无机物如，NO₂^-，O₂，H₂O₂，CO₂等的还原具有电催化效应。对于铁原卟啉在电极表面吸附与反应的研究可以实现对此分子在生物和电催化方面分子水平上的理解，还为实现生物催化和生物传感实用化提供重要依据。衰减全反射表面增强红外光谱（ATR-SEIRAS）和表面增强拉曼光谱（SERS）具有较高的增强信号，是研究自组装分子在表面的吸附取向以及自组装分子与电极表面电子传递的有利表征手段。铁原卟啉的大部分骨架振动模式是拉曼活性的。传统的SERS技术仅限于币类金属，这就限制了SERS对于铁原卟啉功能化界面的研究。SERS表面选律复杂，也不利于判断分子的吸附取向。另外，拉曼光谱对于铁原卟啉与小分子配位研究主要通过骨架振动频率的改变间接推测，不利于表面配位反应特别是与NO和CO等极性小分子配位反应的研究。铁原卟啉外围替代基团羧基的振动是红外活性的，通过研究羧基在金属电极表面的吸附，可以推测铁原卟啉的吸附取向。而且红外光谱对极性小分子很敏感，所以ATR-SEIRAS可方便研究铁原卟啉与NO和CO等极性小分子的表面配位反应。铅酸蓄电池仍然为二次电池中应用范围最广，技术最成熟的化学电源。但由于板栅合金的阳极腐蚀和合金表面的高阻抗的形成使电池放电性能和深充放寿命方面仍存在一些难以解决的问题。板栅的腐蚀性能和合金表面高阻抗层的形成与材料的组成和性质以及表面氧化物膜的生长机理密切相关。我们论文的部分工作是研究阳极膜的生长机理以及筛选合适的材料，进而提高电池性能和延长电池使用寿命。本论文的主要研究结果：一．铁原卟啉自组装层在金电极表面吸附的现场衰减全反射表面增强红外光谱（in situ ATR-SEIRAS）研究铁原卟啉分子是一种重要的功能化分子。我们自行设计了原位衰减全反射表面增强红外光谱（in situ ATR-SEIRAS）附件。本部分工作利用in situ ATR-SEIRAS技术在0.1M HClO₄（pH 1）和PBS（pH 7）溶液中研究了铁原卟啉在Au电极表面吸附状态及随电位的变化情况。选用单晶Si半圆柱作为红外窗口。化学镀方法在Si表面镀一层具有表面增强效应的厚度为60nm金膜。采用直接吸附法在金电极表面组装铁原卟啉分子。由于铁原卟啉是近D_4h结构，根据表面增强红外光谱选律，卟啉环的骨架振动都是非红外活性的，所以在红外光谱上主要观察到环外丙酸基上的羰基振动峰。在0.1M HClO₄溶液中，低电位下的卟啉环外侧的丙酸的主要是以羧酸形式存在，但电位较正时，卟啉环外侧的丙酸的主要存在形式是去质子化的羧基。以上结果表明Au电极表面，随着电位的改变铁原卟啉的吸附状态发生了变化。当电位由负移至较正时，卟啉环的吸附状态由平躺转为大角度倾斜。由于空间位阻的影响铁原卟啉的内酸基中至少一个羧基脱去一个质子，通过静电作用吸附在Au电极表面。状态发生剧烈改变的电位转折点位于0.5V（vs SCE）。在pH 7的溶液中，吸附在Au电极表面的铁原卟啉吸附自组装层与pH 1中观察略有不同。首先，羧酸根的积分强度明显增强，而羧酸的积分强度明显减弱；其次，羧酸和羧酸根随电位发生明显改变的电位移至-0.4V （vs SCE）；再次，在电位大于-0.4V（vs SCE），出现1563 cm^-1处的峰卟啉环外围羧酸根的非对称伸缩振动有关。铁原卟啉的pKa的影响可能是造成两种pH溶液中，铁原卟啉光谱特征不同的原因。二．吸附在金电极表面的铁原卟啉与CO配位反应的现场衰减全反射表面增强红外光谱（in situ ATR-SEIRAS）研究生命过程中，血红蛋白中的铁原卟啉结合一氧化碳会影响与氧的结合，造成细胞缺氧。因此，铁原卟啉与CO的配位反应一直是人们研究的重点。但以前的研究仅限于本体研究。本部分工作利用in situ ATR-SEIRAS研究了0.1M HClO₄溶液中Au电极表面还原态的FePP与CO的表面配位反应。在以FePP／Au为电极（50μM FePP硼砂溶液制）的0.1M HClO₄中通入饱和的CO，在电极表面同时可以观察到五配位的Fe^Ⅱ（CO）PP和六配位Fe^Ⅱ（CO）₂PP。最初电极表面以Fe^Ⅱ（CO）PP为主，随着电位的升高，Fe^Ⅱ（CO）₂PP逐渐增多。Fe^Ⅱ（CO）₂PP相当稳定，即使在较高电位（0.8V（vs SCE））也没有氧化完全。这种五配位的Fe^Ⅱ（CO）PP和六配位Fe^Ⅱ（CO）₂PP在表面的出现以及比例随电位变化主要是由于FePP在Au电极表面的吸附取向随电位变化引起。结合红外光谱图和电化学研究发现，Fe^Ⅱ（CO）PP氧化到Fe^Ⅲpp的实质是CO首先从Fe^Ⅱ（CO）PP中解离出来，然后Fe^ⅡPP氧化成Fe^ⅢPP，其中间转换电位为0.09V（vs SCE）。换作铁原卟啉丙酮饱和溶液制得的FePP／Au为电极的体系中，其红外谱图与上文中的有极大不同。FePP环外围替代基团羧酸和羧酸根没有在谱图中出现，取而代之的是代表卟啉坏骨架振动的一些红外活性的峰，这些峰也随电位的移动而发生变化。而代表Fe^Ⅱ（CO）PP的峰变得很弱，并没有观察到Fe^Ⅱ（CO）₂PP的存在，这可能在某种程度上反映了丙酮与铁原卟啉的配位。三．吸附在金电极表面的铁原卟啉与NO配位反应的现场衰减全反射表面增强红外光谱研究（in situ ATR-SEIRAS）NO是一种在生命科学及环境催化方面有非常重要作用的分子。NO是神经传导的重要信息物质，还能引起血管舒张。另外，铁原卟啉作为催化剂能够催化NO₂^-的分解。所有这些作用机理都与NO和铁卟啉的配位息息相关。但关于铁原卟啉与NO的配合很复杂，Fe（Ⅲ）和Fe（Ⅱ）都可以与NO配位，还存在多种等电子体。特别是Fe（Ⅱ）与NO配合物中NO振动在红外光谱中出现的位置与H₂O的剪式振动很相近，给相应的判断带来一定的困难。本文采用原位衰减全反射表面增强红外光谱（in situ ATR-SEIRAS）法研究了0.1M HClO₄中Au电极表面FePP自组装层与NO的配位反应以及NO与CO在铁原卟啉自组装层表面的交换反应。通过控制电位测量NO与FePP配位前后的原位红外光谱以及改变电位利用原位红外光谱研究其配位过程结合的方法，测定了Au电极表面铁原卟啉亚硝酰配合物的种类以及随电位变化情况。在较高电位出现三价铁原卟啉与NO的配合物，其特征峰出现在1915 cm^-1，存在电位区间较窄且不稳定容易分解。其结构至认为是Fe^Ⅲ（NO）（OH₂）PP或其等电子体Fe^Ⅱ（NO）⁺（OH₂）PP。两个较低频率出现的峰为二价铁原卟啉与一氧化氮的配合物的特征峰，可以在很宽的电位范围稳定存在。其中一个具有不明显Stark效应的位于ca．1670cm^-1，指认为二价铁原卟啉的单亚硝酰配合物Fe^Ⅱ（NO）PP。另一个具有明显Stark效应的位于ca．1710 cm^-1，指认为二价铁原卟啉的双亚硝酰配合物Fe^Ⅱ（NO）₂PP。这种同时存在两种铁原卟啉亚硝酰配合物主要是由于铁原卟啉在Au电极表面组装的不均一性引起。在含有NO的溶液中通入饱和CO发现，NO与FePP的结合抑制了CO与Fe^ⅡPP的配位。只有在-0.2V（vs SCE），铁原卟啉亚硝酰化合物被还原，NO与铁原卟啉分离的情况下，CO才能与Fe^ⅡPP配位。同样的，-0.1V（vs SCE）在饱和CO溶液中，通入NO 1min，我们发现，CO全部被NO取代，这在另一方面也证实了我们的上述判断。在整个交换过程中，我们并没有观察到代表卟啉环外围的羧酸和羧酸根的红外特征峰，这说明交换反应的发生并不会引起卟啉环吸附取向的转变。四．铁原卟啉在铂表面的现场振动光谱法研究有关Au或Ag表面通过巯基固定分子而构建功能化界面的研究已有大量报道。为了拓展功能化界面研究，将铁原卟啉分子（FePP）组装在Pt表面也是我们论文的研究目标之一。SERS主要得到铁原卟啉的骨架振动的信息，而SEIRAS则有利于研究极性配体和卟啉环外围替代基团。本文结合SERS和SEIRAS研究了0.1M HClO₄溶液中FePP在Pt表面的吸附行为。粗糙的Pt是一种非传统，弱SERS效应的金属。我们利用SERS研究了FePP分子在粗糙Pt电极上的吸附取向以及随电位的变化。粗糙度为101的Pt表面的增强因子为665，在这种增强条件下可以很清楚的观察到FePP分子的骨架振动信息。FePP主要采取近乎垂直方式吸附，其骨架振动模式的随着电位的变化反映了中心铁离子价态的变化。对标志铁原卟啉中心价态变化的ν₄峰强度积分拟合可得Fe³⁺／Fe²⁺的中间转换电位为-0.2 V（vs SCE）。表面增强红外光谱的研究发现环外羧酸和羧酸根同时吸附在Pt电极表面。通过对光谱的分析得出卟啉环几乎垂直吸附在电极表面。与Au电极表面FePP的吸附行为不同，环外围羧酸和羧酸根的特征峰基本不随着电位改变而发生移动，这可能与电位采集范围有关。所以，综合拉曼光谱和红外光谱的信息，FePP在Pt表面的吸附模式主要采取近乎垂直吸附模式。我们还利用表面增强拉曼效应研究了pH 3和pH 7溶液中FePP在Pt表面的吸附行为。大部分骨架振模式随电位变化与pH1溶液中观察到的研究结果相似。只是Fe³⁺／Fe²⁺中间转换电位随pH增大会发生负移。五．硫酸溶液中铅电极上阳极Pb（Ⅱ）膜的阳极极化以及稀土元素Yb的添加对铅电极上阳极Pb（Ⅱ）膜以及PbO₂生长的影响阳极膜Pb（Ⅱ）膜生长电位0.9V接近于阀控式铅酸电池（VRLA）电池在深放电条件下正极板栅所处的电位，其主要组成为PbO，PbO·PbSO₄和PbSO₄。通过对硫酸溶液中铅电极上阳极Pb（Ⅱ）膜的阳极极化的研究我们主要得出以下结论：（1）Pb电极上阳极Pb（Ⅱ）膜的极化主要是由电荷传递过程造成的。（2）Pb电极在H₂SO₄溶液中遵循如下的溶解-沉淀机理以生长PbO膜：（1） Pb+OH^-→Pb（OH）_ad+e^-；（2） Pb（OH）_ad+OH^-→PbOOH^-+H⁺+e^-（rds）；（3） PbOOH^-→PbO+OH^-。Yb具有磁性、荧光激活、无记忆效应的等优点而广泛用作工业添加剂。根据溶解沉积机理，其饱和溶解度与PbOOH^-相近，我们希望Yb的添加可以改善Pb阳极膜的性质。Yb的添加可使Pb合金上于0.9V下生长的阳极Pb（Ⅱ）膜阻抗明显下降，并使Pb（Ⅱ）膜的生长速度明显减小。通过对其机理的研究发现PbO区发生阳极腐蚀时，部分的Yb³⁺较PbOO^-更沉积于基体表面，Yb（OH）₃覆盖在阳极膜内，阻碍了基体与溶解的离子传递，当膜内PbOOH^-的浓度达到饱和时，PbO与Yb（OH）₃也将在膜内更深处发生共沉积，形成共沉积层，从而抑制Pb（Ⅱ）膜的生长。而在1.4V下生长的阳极膜，其主要组成为α-PbO₂和β-PbO₂，Yb的添加可明显抑制β-PbO₂生长但促进了α-PbO₂的生长。对于膜阻抗的研究，发现Yb的添加可抑制PbO合金1.4V下的氧化。更多还原

【Abstract】 Surface electrochemistry is a rapidly growing inter-discipline of surface scienceand electrochemistry. A recent hot topic in surface electrochemistry is the interfacialbioelectrochemistry which involves the construction, characterization and utilizationof bioactive electrode surfaces modified with functional biomolecules and theirrelated model compounds. These functional electrode/electrolyte interfaces providenot only platforms for the study of the electron transfer but also for the potentialapplications in electrocatalysis and bio-sensing.Metalloporphyrins exist in many organisms as prosthetic groups of proteins.Specifically, iron protoporphyrinⅨ（simplified as FePP） is the common active centerof myoglobin, hemoglobin, cytochrome C and peroxide enzymes. FePP has manyimportant functions such as transportation and biocatalysis in vivo. Recent years,FePP modified electrodes were found to exhibit excellent electrocatalytic effects onthe reduction of dioxygen, hydrogen peroxide, nitrite, carbon dioxide and so on. Thestudy of potential dependent structure and reaction of FePP adlayer at electrodes notonly helps to understand its biocatalytic functions at molecular level but also lay thebasis for this functional electrode to be used in catalysis and sensing aspects.ATR-surface enhanced IR absorption spectroscopy （ATR-SEIRAS） and surfaceenhanced Raman spectroscopy （SERS） have high surface sensitivity which willfacilitate in situ monitoring of surface adsorption and reaction. Most of the skeletalvibrations of FePP are Raman-active. Strong SER effects are produced mainly oncoinage metals which limited the study of versatile functional surfaces with FePP.The complicated surface selection rule of SERS makes it difficult to deduce theadsorption configuration of adsorbates. Further more, it is quite difficult if notpossible to obtain directly the binding information of small ligands toward FePPadlayer by SERS which can only be judged by the change in relative intensities ofporphyrin ring bands. SEIRAS is very sensitive to the highly polar small molecules,including CO and NO, facilitating the study of surface coordination of FePP with COor NO. In addition, SEIRAS is also suitable for detecting the peripheral propionicand propionate groups of FePP adlayer, thus may help to understand the adsorptionconfiguration of this molecule. So far, lead acid batteries remain the most frequently used batteries of all with itshigh performance-price ratio, secure and reliable operation. However, the seriousanodic corrosion and the high impedance layer formed on surface of the grid alloy arethe main factors to affect the discharge performance and deep charge/discharge cyclelife of the batteries. The formation of the high impedance layer is related to thecomposition and the properties of the alloy, as well as the growth mechanism of theanodic oxide film formed on the alloy. It is part of our thesis work to study the growthmechanism of anodic film and select the suitable alloying elements from rare-earthmetals to tackle the anodic corrosion problem.The main results and conclusions of the dissertation are summarized as follows:（Ⅰ） In situ ATR-SEIRAS study on FePP adlayer self-assembled on a Au electrodeIn situ ATR surface enhanced IR absorption spectroscopy （ATR-SEIRAS） wasfirstly applied to probe potential dependent adsorption configuration of FePP adlayeron Au （FePP/Au） electrodes in 0.1 M HClO₄ （pH 1） and PBS （pH 7）.A SEIRA-active Au nanoparticle film （ca. 60-nm-thick） was deposited on thetotal-reflecting plane of hemicylindrical Si prism with electroless plating method. TheFePP adlayer immobilized on Au nanoparticle film by soaking the latter in a basicsolution containing dilute FePP as the working electrode.FePP is of approximately D_4h symmetry structure, IR-active in-plane stretchingvibrations of porphyrin ring skeleton are very weak, only the peripheral propionicacid groups of FePP can be observed in pH 1 solution. At lower potentials, statistically,two peripheral propionic acid groups predominate, FePP mainly lie nearly flat on theAu surface; while at higher potentials, one of them is deprotonated with its twooxygen atoms attached on Au surface, yielding a kind of reorientation （tilting） of theporphyrin ring. The steric hindrance probably prevents the simultaneous adsorption oftwo carboxylate groups on Au surface even at higher potentials.Slight different spectral features can be found at pH 7. Firstly, the band forperipheral propionate groups is much stronger at higher potentials at pH 7; Secondly,the porphyrin ring may re-orientate to a relatively large extent by tilting up ring planethrough anchoring a carboxylate group on the metal surface at ca. 0.5 V at pH 1 and-0.4 V at pH7, respectively; Thirdly, the band 1563 cm^-1, assigned toν_asCOO-,appeared at the potential higher than -0.4 V at pH 7. Chemical dissociation based on pKa of the two peripheral propionic acid groups at pH 7 may also contribute to thedifferent spectral features observed.（Ⅱ） in situ ATR-SEIRAS on CO adducts of FePP adlayer self assembled on a AuelectrodeCoordination chemistry of CO with metalloporphyrins is a biologically andchemically important topic as promoted by the interest in comparing the coordinationproperties of metalloporphyrins with heme proteins. Historically, studies on CObinding with metalloporphyrins were mainly limited to bulk phase reactions.The surface coordination chemistry of carbon monoxide with the reduced form（Fe^ⅡPP） of iron（Ⅲ） protoporphyrinⅨ（Fe^Ⅲpp） monolayer self-assembled on a Auelectrode in 0.1 M HClO₄ was studied for the first time by using in situ ATR- surfaceenhanced infrared absorption spectroscopy （ATR-SEIRAS）.Both mono- and bis- carbonyl adducts [simplified as Fe^Ⅱ（CO）PP andFe^Ⅱ（CO）₂PP, respectively] were detected on the FePP/Au（prepared with 50μMFePP in 0.1M borax）, depending on the history of potential control. Initially theFe^Ⅱ（CO）PP predominates, and the intermediate transition potential for the conversionof Fe^Ⅱ（CO）PP to Fe^ⅢPP and CO was spectrally determined to be ca. 0.09 V （vs. SCE）.The ratio of Fe^Ⅱ（CO）₂PP and Fe^Ⅱ（CO）PP increases after a potential excursion to asufficiently positive value. Fe^Ⅱ（CO）₂PP is much more stable against itselectro-oxidation to Fe^ⅢPP than its counterpart Fe^Ⅱ（CO）PP with increasing potential.The observed change of coordination properties may be ascribed to an irreversiblestructural reorganization of the FePP adlayer caused by the potential excursion.The great difference of adsorption of FePP on Au can be found with FePP/Auprepared with saturated FePP in acetone. Several relative weak IR-active in-planestretching vibrations of porphyrin ring skeleton can be observed instead of theperipheral propionic acid groups. Fe^Ⅱ（CO）PP can also be found but rather weak, nopeaks ascribed to Fe^Ⅱ（CO）₂PP can be observed with this method, suggesting thestrong coordination of acetone to FePP.（Ⅲ） in situ ATR-SEIRAS on NO adduets of FePP adlayer self assembled on aAu electrodeNitric oxide is unique among diatomic molecules in that it can bind to manymetals of different oxidation states and different electron configurations. The coordination chemistry of NO with iron porphyrins has been intensively investigated,inspired by both fundamental and technological interests ranging from relevantbiological functions including vasodilatation and neuronal communication toenvironmental concerns about （bio）catalytic reduction and oxidation of nitrites. TheNO coordination with FePP/Au is complicated: first, NO can coordinate to both ferricand ferrous protoporphyrins; second, multiple isoelectronic forms are present for aNO adducts of either ferric or ferrous protoporphyrin; third,ν_N-O of NO coordinatedto Fe^Ⅱpp is close toδ_HOH of water andν_C-O of peripheral carboxylic groups, and thusshould be dealt with care.Based on potential controlled ATR-SEIRAS on independent FePP/Au electrodesand multi-step ATR-SEIRAS measurement on one same FePP/Au electrode, for thefirst time, up to three IR bands corresponding to three types of nitrosyl adducts ofFePP have been identified with their intensities （concentrations） varied with thepotential applied. The 1915 cm^-1 band, which shows up at relatively positivepotentials and stabilizes in a rather narrow potential range can be reasonably assignedto the Fe^Ⅱ（NO）（OH₂）PP species or its isoelectronic format Fe^Ⅱ（NO）⁺（OH₂）PP. Theother two bands with much lower frequencies, which can stabilize over a much widerpotential range and exhibit nearly opposite potential dependent intensities, arebasically characteristic of nitrosyl adducts of ferrous FePP. One band at ca. 1670 cm^-1with insignificant Stark effect, can be attributed to Fe^Ⅱ（NO）PP. The other above 1705cm^-1 with significant Stark effect, could be ascribed to Fe^Ⅱ（NO）₂PP. The multi nitrosyladductions may be caused by the largely inhomogeneous structure of the FePP adlayeron Au electrodes.The exchange of NO and CO on FePP/Au in 0.1M HClO₄ are brieflyinvestigated. Stronger binding of NO with FePP adlayer prevents the CO coordinationwith the latter, and the formation of Fe^Ⅱ（CO）PP was only found at potentials negativeof -0.2V where Fe^Ⅱ（NO）PP is partially reduced. The exchange of CO and NO onFePP/Au in 0.1M HClO₄ didn’t arouse the change of adsorption orientation of FePPon Au surface.（Ⅳ） in situ SERS and in situ ATR-SEIRAS study of iron protoporphyrinmonolayer adsorption on polycrystalline Pt electrodeSelf-assembly of molecules including thiols and porphyrins on Au and Agelectrodes has been intensively studied. To broaden the types of functional electrodes,FePP self-assembled on Pt electrode is among the targets of our thesis work. SERS is suitable for detecting the skeletal vibrations of FePP adlayer whereas SEIRAS is goodfor detecting polar ligands and peripheral groups of FePP adlayer. For the first time,both in situ SERS and in situ ATR-SEIRAS were applied to probe adsorption of FePPadlayer on Pt electrodes in 0.1 M HClO₄.The potential dependent SERS spectra of FePP adlayer with the enhanced factornearly 10³ were acquired on a roughened Pt electrode. Analyses of spectral datarecorded at pH1 over a wide potential region made it possible to obtain potentialdependent adsorption isotherms, from which the stranded redox potential was foundto be ca. -0.2 V. Up-tilted orientation of FePP on Pt electrode was assumed based onin situ SERS and in situ ATR-SEIRAS measurements. Unlike FePP on Au electrode,FePP on Pt electrode hardly reorients within the potential range investigated.SERS was also extended to the measurements of FePP adsorption on roughenedPt electrode performed in pH 3 and pH 7 solutions （PBS）. The intermediate transitionpotential of Fe³⁺/Fe²⁺ moves to a lower potential at higher pH.（Ⅴ） Study of polarization behavior of the anodic Pb（Ⅱ） film on Pb eletrode andthe effect of alloying element Yb on the growth of anodic Pb（Ⅱ） and PbO₂films on Pb alloy electrode in 4.5 M H₂SO₄The anodic polarization behavior of anodic Pb（Ⅱ） film preformed on Pbelectrode was studied by using fast speed linear sweep voltammetry （LSV）,electrochemical impedance spectroscopy and （EIS） scanning electron microscope（SEM）. The mechanism of the formation of the anodic PbO film is suggested asfollows: （1） Pb+OH^-→Pb（OH）_ad+e^-; （2） Pb（OH）_ad+OH^-→PbOOH^-+H⁺+e^-（rds）; （3）PbOOH^-→PbO+OH^-.The anodic Pb（Ⅱ） films formed on Pb and Pb-Yb electrode at 0.9V （vs Hg/Hg₂SO₄） in sulfuric acid solution were studied. The results showed that the additionof Yb can decrease the value of Z’ for the anodic Pb（Ⅱ） film and inhibit the growth ofthe film. According to above mechanism proposed for the formation of the anodicPbO film, the inhibition effect of this alloy element can be explained as follows: thesaturated concentration of Yb³⁺ is far smaller than that of PbOOH^-, so Yb³⁺ willprecipitate earlier than PbOOH^- at the innermost of film. Once the concentration ofPbOOH^- is close to the saturated concentration of Yb³⁺, PbOOH^- will co-precipitatewith Yb³⁺ at the innermost of film, inhibiting the film growth.The study of anodic PbO₂ film （α-PbO₂ andβ-PbO₂） formed on Pb-Yb electrode at the deep charge potential of 1.4 V in sulfuric acid solution was carried out. Theresults showed that the addition of Yb can promote the growth ofα-PbO₂ but inhibitthe growth ofβ-PbO₂. The growth of PbO under-layer can be inhibited at 1.4V asjudged from the impedance decease after alloying Pb with Yb.更多还原