蒽醌/聚吡咯复合膜修饰电极的电化学行为和电催化活性

在水溶液中制备了掺杂蒽醌磺酸盐(AQS)的聚吡咯(PPy)/玻碳复合膜修饰电极,采用循环伏安法和旋转圆盘电极技术研究了该修饰电极在不同pH值溶液中的电化学行为以及在pH=5.5的磷酸盐缓冲溶液中对氧还原反应的电催化性能和动力学.结果表明,与裸玻碳电极相比,PPy膜的存在不仅降低了AQS的反应电位和峰电位差,而且增大了其氧化还原反应的峰电流,H2AQ/HAQ-氧化还原对的电离常数为9.5.AQS/PPy膜修饰电极上氧的还原主要是两电子还原为H2O2的不可逆过程,H2AQ对氧还原反应起主要催化作用,还原过程符合异相氧化还原催化机理.该修饰电极具有良好的电化学重现性.     

不同状态下聚吡咯膜的电化学阻抗

用恒电流法分别聚合了掺杂对甲苯磺酸根(pTS-)和十二烷基磺酸根(DS-)的聚吡咯膜(PPy/pTS和PPy/DS),通过循环伏安法(CV)和电化学阻抗法(EIS)测试了聚吡咯膜在NaCl溶液中‘过电位’电化学过程前后及不同电位下聚吡咯膜的电化学性能.同时,通过嵌入和脱出Na+和Cl-离子的聚吡咯膜在特定溶液中电化学阻抗图谱,研究了离子的嵌入对聚吡咯膜电化学性能的影响.结果表明‘过电位’现象可以提高聚吡咯膜的离子电导率和膜电容,Cl-离子的嵌入能提高PPy/pTS的电导率,而Na+离子的嵌入对聚吡咯膜的电导率影响不大.另外,嵌入离子对聚吡咯膜形貌的改变会对聚吡咯膜的离子传导率有一定影响,从而导致膜的电化学阻抗的变化.     

过渡金属配合物阴离子嵌人聚吡咯膜电极的表征

采用电化学聚合方法在水溶液中制备出Fe(CN)_6~(4-)嵌入的聚吡咯膜修饰电极, 电极具有稳定的Fe(CN)_6~(4-)/Fe(CN)_6~(3-)电化学响应, 其氧化、还原电位与电解质溶液中H~+浓度有关。借助XPS、IR和ESR方法对聚合物膜结构进行表征, 探讨嵌入物种Fe(CN)_6~(n-)和聚吡咯之间的相互作用, 提出一种可能的轨道相互作用模式。     

采用连续电位阶跃方法研究聚吡咯在电解质水溶液中的氧化还原稳定性

连续电位阶跃方法是一种研究氧化还原稳定性的有效方法. 本文采用连续电位阶跃方法研究了以对甲苯磺酸钠为掺杂剂的聚吡咯(ppy)膜的电化学氧化还原稳定性, 通过计算聚吡咯在阶跃电位下的还原电量(Q_red), 还原和氧化电量的比值(Q_red/Q_ox)考察聚吡咯在H₂SO₄、Na₂SO₄和NaOH溶液中在不同电位下的氧化还原可逆性. 结果发现聚吡咯过氧化的发生强烈依赖支持电解质的pH值和阶跃电位. 在H₂SO₄溶液中, 过氧化的起始电位为0.8 V, 而在Na₂SO₄溶液中, 过氧化的起始电位为0.5 V. 在NaOH溶液中, 过氧化在任何电位均可发生, 表明溶液中OH^- 的存在是过氧化发生的直接原因.     

过氧化聚吡咯膜修饰电极检测肾上腺素研究

报道了肾上腺素(EP)在过氧化聚吡咯膜(OPPy)修饰电极上的电化学行为及其测定方法。过氧化聚吡咯膜(OPPy)修饰电极对EP的氧化还原具有良好的催化作用,并具有较高的选择性。在最佳实验条件下,EP的还原峰电流与其浓度在2×10-7~5×10-4mol.L-1范围内呈良好的线性关系,相关系数为0.999 9,检出限为8×10-8mol.L-1。将该电极应用于EP实际样品的测定,效果良好。     

氧化铜-过氧化聚吡咯-还原氧化石墨烯复合膜修饰电极非酶检测葡萄糖

先以氧化石墨烯(Graphen oxide,GO)为阴离子掺杂剂,采用电化学聚合法制备了聚吡咯-氧化石墨烯复合膜(PPy-GO)。分别在0.10 mol/L Na Cl和0.10 mol/L NaOH溶液中对其进行还原和过氧化处理,制得过氧化聚吡咯-还原氧化石墨烯复合膜(OPPy-ERGO)。再以此OPPy-ERGO复合膜为载体,采用电化学沉积法制备了氧化铜-过氧化聚吡咯-还原氧化石墨烯复合膜修饰电极(CuO-OPPy-ERGO/CCE)。通过扫描电镜和电化学方法对此电极进行表征,研究了葡萄糖在此修饰电极上的电化学行为。结果表明,此电极对葡萄糖的电氧化过程表现出高的催化活性和良好的抗干扰能力。在0.20 mol/L NaOH溶液中,安培法检测葡萄糖的线性范围为5.0×10~(-7)~1.0×10~(-3)mol/L,检出限(3Sb)为2.0×10~(-7)mol/L,灵敏度为121.8μA/(mmol·L~(-1))。该电极用于血清中葡萄糖含量的测定,加标回收率为96.0%~110.1%。     

聚吡咯对Cu(II)的催化还原作用

以对甲苯磺酸钠为掺杂剂在不锈钢(SS)电极表面恒电位合成聚吡咯(PPy)修饰膜, 采用恒电位和动电位对Cu(II)的还原效果进行了研究, 并与不锈钢电极进行了对比. 结果表明, 由于聚吡咯的催化作用, 聚吡咯修饰电极对Cu(II)还原效率高于不锈钢电极; 聚吡咯膜对析氢有明显的抑制作用, 因此电流效率远远高于不锈钢电极, 这是采用聚吡咯进行电化学还原的明显优势. 通过在不同浓度Cu(II)酸性溶液中的循环伏安行为讨论了聚吡咯对Cu(II)的还原作用机理.     

硝苯地平在聚吡咯膜修饰电极上的电化学行为及电位溶出分析

提出了在吡咯的聚合过程将硝苯地平掺杂富集进聚吡咯膜中 ,然后在合适的溶液中通过线性扫描将之溶出的分析方法。与空白聚吡咯修饰电极 (PPy-GCE)比较 ,在0.088mol/LH2O2-0.1mol/LH2SO4 底液中 ,以100mV/s的速率进行线性扫描时 ,硝苯地平有一灵敏的线性扫描溶出峰 ,峰电位在 -0.628V(vs.SCE)。峰电流与硝苯地平的浓度在1×10 -8～1×10 -4mol/L范围内有良好的线性关系 ,利用这一峰对硝苯地平片剂的含量进行了测试 ,分析结果令人满意     

酸性介质中碘离子在铂电极上的电化学氧化行为

采用循环伏安法研究了酸性介质中碘离子在铂电极上不同电位区间, 不同酸度下的电化学反应行为. 结果表明, 当极化电位较低(小于0.6 V(vs Hg/Hg2SO4))时, 碘离子在铂电极上发生2I--2e→I2电氧化反应, 反应产物通过I2+I-=I-3被进一步溶解, 整个反应属于E-C(electrochemical-chemical)模式. 电氧化过程中可以形成碘膜, 其也可以被碘离子溶解. 当极化电位升高至0.6 V(vs Hg/Hg2SO4)或以上时, 碘离子会直接电氧化为高价态碘化合物, I-+3H2O→IO-3+6H++6e, 而析出的碘膜并不发生再氧化反应; 在电化学还原过程中, 出现了两个还原峰, 分别对应于I2、I-3的还原反应; 在无碘膜时, 碘离子电氧化过程受溶液中碘离子的液相扩散步骤控制; 碘膜形成后, 主要受碘膜中碘离子的固相扩散控制; 酸度对于碘离子的电化学氧化过程有很大的影响, 其线性极化曲线的起峰电位及电流峰值电位均随酸浓度升高而负移.     

双-Keggin型四元杂多化合物[Nd(SiMo7W4O39)2]13-多层膜在化学修饰玻碳电极上的组装及电催化

报道双-Keggin型四元杂多化合物K10H3[Nd(SiMo7W4O39)2]XH2O(简称[Nd(SiMo7W4)2]^13-）聚合物的交替组装多层膜在4-氨基苯甲酸修饰玻碳电极上的制备及其电化学特性。各层的循环伏安行为证明膜的均匀增长，峰电流随层数的增加而增加，与溶液中的电化学行为相比，位于多层膜中的杂多化合物的氧化还原特征峰随着多层膜层数的增加，具有一定程度的形变。该电极具有较高的稳定性。并讨论了pH对其氧化还原行为的影响，考察了该多层膜修饰电极对BrO3^-、HNO2和H2O2等的电催化性能。     

Scanning electrochemical microscopy in combination with piezoelectric quartz crystal impedance analysis for studying the growth and electrochemistry as well as microetching of poly(o-phenylenediamine) thin films

The combination of scanning electrochemical microscopy (SECM) with piezoelectric quartz crystal impedance (PQCI) analysis was proposed as a novel multiparameter method for investigating the cyclic voltammetric growth of poly(o-phenylenediamine) (PoPD) thin films at Au electrodes in aqueous solutions of various pH values and the potentiostatic microetching (localized degradation) of these films in 0.10 mol/L aqueous H2SO4 for comparative examinations on polymer porosity and stability. Two potential-sweep ranges, -0.4 to 0.9 (I) and 0 to 0.9 (II) V versus SCE, and four solutions, acidic (A, 0.20 mol/L H2SO4 + 0.10 mol/L Na2SO4; B, 0.10 mol/L H2SO4 + 0.20 mol/L Na2SO4), neutral (C, 0.10 mol/L PBS + 0.20 mol/L Na2SO4, pH 7.2), and alkaline (D, 0.20 mol/L NaOH + 0.20 mol/L Na2SO4) aqueous solutions, were selected for PoPD growth. The pH increase for the polymerization solution increased the molar percentage of polyaniline-like chains in PoPD, as quantified from the current peaks at approximately 0.6 V versus a saturated calomel electrode (SCE) for the oxidation of -NH2 groups in as-prepared PoPD (grown from solutions C and D) during their redox switching in 0.10 mol/L aqueous H2SO4 for the first time. The unusual PQCI responses observed at negative potentials (potential range I) in the first several potential cycles during the cyclic voltammetric growth of PoPD in acidic and neutral solutions have been reasonably explained as being due to the precipitation/dissolution of the poorly soluble phenazinehydrine charge-transfer complexes developed during redox switching of oligomers for the first time, which brought about much less compact PoPD films and their higher degradability than those grown in the same solution but over potential range II. SECM, scanning electron microscopy (SEM), and piezoelectric quartz crystal (PQC) frequency were used to estimate the sizes of etched microscale spots. In addition, the x-, y-, or z-axis movement of a Pt microelectrode of 25-mum diameter near the PQC electrode was found to influence negligibly the PQCI responses in 1.0 mol/L aqueous Na2SO4 containing K4Fe(CN)6 up to 0.10 mol/L, and a new protocol of dynamically electrodepositing silver microwires via the chemical-lens method was proposed for examining the local mass-sensitivity distribution on the PQC surface.     

Structure and electrochemistry of 4,4'-dithiodipyridine self-assembled monolayers in comparison with 4-mercaptopyridine self-assembled monolayers on Au(111)

4,4'-Dithiodipyridine (PySSPy) monolayers on Au(111) were investigated by cyclic voltammetry, X-ray photoelectron spectroscopy (XPS) and in situ scanning tunneling microscopy (STM). The studies were performed in solutions of different anions and pHs (0.1 M H2SO4, 0.1 M HClO4, 0.1 and 0.01 M Na2SO4, 0.1 and 0.01 M NaOH). The cyclic current-potential curves in H2SO4 show current peaks at about 0.4 V, which are absent for all other electrolytes at this potential. The XPS data suggest that PySSPy adsorbs via the S endgroup on the gold surface and the S-S bond breaks during adsorption. From the chemical shift of the N(ls) peak, it is concluded that in acidic media the self-assembled monolayer (SAM) is fully protonated, whereas in basic solution it is not. The pKa is estimated to be 5.3. STM studies reveal the existence of highly ordered superstructures for the SAM. In Na2SO4 and H2SO4, a (7 x mean square root of 3) structure is proposed. However, whereas in Na2SO4 solutions the superstructure does not change with potential, in 0.1 M H2SO4 the superstructure is observed only negative of the current peak at +0.4 V. At more positive potentials, the film becomes disordered. The results are compared to those for 4-mercaptopyridine (PyS) SAMs. XPS experiments and current-potential curves indicate that both molecules adsorb in the same manner on Au(111), that is, even in the case of PySSPy the adspecies is PyS. The STM results, however, call for a more subtle interpretation. While in Na2SO4 solutions the observed superstructures are the same for both SAMs, markedly different structures are found for PySSPy and PyS SAMs in 0.1 M H2SO4.     

Perchlorate interchange during the redox process of PPy/PVS films in an acetonitrile medium. a voltammetric and EDX study

Polypyrrole/poly(vinyl sulfonate) (PPy/PVS) films in acetonitrile containing 0.1 M LiClO4 were studied by cyclic voltammetry. Consecutive voltammograms pointed to a continuous increase in the charge involved in the process, suggesting a rise in the number of the electroactive participants involved in the redox process. However, voltammograms obtained for the PPy/ClO4 films in analogous conditions pointed to a steady-state behavior from the very early cycles. Theoretical studies based on the Nernst and Butler-Volmer equations indicated that perchlorate ions are involved during the oxidation/reduction process of the PPy/PVS films when the steady state is reached. This result was confirmed by "ex situ" energy-dispersive X-ray analysis of the films. In this regard, the electrochemical behavior of PPy/PVS polymers was similar to that of PPy/ClO4 films when a high number of cycles were carried out. The exchange of ClO4- during the redox reaction of the PPy/PVS films made it necessary to incorporate Li+ cations inside the polymer during the initial voltammetric cycles to compensate for the negative charges of PVS polyanions. Li+ cations are mainly stabilized inside the polymer by the ion pairs formed with the sulfonated groups of the PVS. An increase and shift of the voltammetric cycles indicated a restructuring of the polymeric chains with consecutive scans.     

电解质溶液对聚吡咯电聚合中过氧化行为的影响

分别以硫酸/水和高氯酸锂/乙腈为电解质溶液, 采用循环伏安法在铂基底电极上电聚合制备了聚吡咯, 研究了电解质溶液对聚吡咯电聚合过程中过氧化行为的影响. 与硫酸/水溶液相比, 在高氯酸锂/乙腈溶液中电聚合制备的聚吡咯发生过氧化的峰电位正移了0.42 V. 采用原位傅里叶变换红外(in situ FTIR)光谱技术检测, 结果表明, 电聚合制备的聚吡咯在2种电解质溶液中均发生了过氧化反应, 其β-C经氧化生成C-OH或CO. 在硫酸/水溶液中, 部分聚吡咯发生电氧化降解生成CO₂, 致使其共轭结构被破坏, 电导率迅速下降. 而在高氯酸锂/乙腈溶液中, 在更高的电位范围内, 聚吡咯并没有氧化降解成CO₂.     

甲酸在钼青铜修饰铂电极上的催化氧化

应用循环伏安法和双电位阶跃法研究了不同浓度硫酸中钼酸盐在多晶铂电极上的电化学行为 .在硫酸溶液中 ,当电位负向扫描时 ,钼酸盐即于铂电极上还原形成钼青铜 ,吸附在电极表面 ;电位正向扫描时钼青铜将再被氧化 ,氧化机理受硫酸浓度的影响 .铂电极因钼酸盐的还原和钼青铜的氧化而得到修饰 .在硫酸钠溶液中以此修饰的铂电极对甲酸氧化有明显的催化作用 ,其氧化峰电流接近未修饰铂电极上的 2倍 .钼青铜对铂的不完全修饰或过分修饰均会减弱甲酸氧化的催化作用     

Preparation, structure, and electrochemistry of a polypyrrole film doped with manganese(III)-substituted Dawson-type phosphopolyoxotungstate

The fabrication, structure, electrochemical properties, and electrocatalytic properties of a manganese(III)-substituted Dawson-type phosphopolyoxotungstate, alpha 2-K7P2W17O61(Mn3+.OH2).12H2O (P2W17Mn), entrapped in polypyrrole (PPy) film have been studied. The hybrid film was prepared by potentiostatic polymerization from aqueous solution containing 20 mM pyrrole (Py) and 2 mM P2W17Mn on a pyrolytic graphite (PG) surface. Chronoamperometry, Raman spectroscopy, UV-visible absorption spectroscopy, and cyclic voltammetry were used to monitor and characterize the growth, structure, and properties of the film. The chronoamperometric curve shows that P2W17Mn can catalyze the electrochemical polymerization of Py. The Raman spectrum suggests that the doped P2W17Mn has little effect on the structure of PPy film. The P2W17Mn/PPy film exhibits good voltammetric response in both the acidic aqueous and acetonitrile solutions. At pH 1.0, the molar ratio of pyrrole to P2W17Mn7- in the hybrid film is 21.1:1, quite close to the expected ratio of 21.2:1 for a PPy film with a +0.33 oxidation level per pyrrole moiety and doped with an anion with a charge of 7. The influence of solution pH on P2W17Mn7- in the film is much smaller than that in the aqueous solution. During the potential scanning in 0.1 M LiClO4 acetonitrile solution, P2W17Mn7- was slowly released from the hybrid film and electrolyte ions (Li+ and ClO4-) were inserted into the film. This was identified by cyclic voltammetry and UV-visible spectroscopy. Additionally, the hybrid film can effectively catalyze the reduction of hydrogen peroxide and nitrite.     

Keggin型缺位硅钨杂多阴离子的电化学性质及电催化还原H2O2

应用循环伏安、方波伏安和交流阻抗法研究了Keggin型缺位硅钨杂多阴离子SiW11O398-(SiW11)在0.1mol.L-1NaHSO4+Na2SO4溶液中的电化学性质及其对H2O2还原的间接电催化作用.结果表明,SiW11的酸性水溶液在玻碳(GC)电极上显示两对可逆的还原-氧化波,对应的电荷迁移数均为1,且有2个质子参与反应.根据第1对波的还原峰电流与扫描速率平方根关系得到SiW11在溶液中的扩散系数DO为8.92×10-6cm2.s-1.SiW11对H2O2的还原具有明显的电催化活性,催化峰电位随溶液pH的降低而正移,峰电流增大.质子H+在催化反应中起协同促进作用.实验测定该电催化过程的均相准一级反应速率常数为0.30 s-1.SiW11电催化还原H2O2的机理被认为是经过形成所谓"七配位过氧化物"而发生的.