聚合溶液pH值对染料敏化太阳电池中聚吡咯对电极结构和性能的影响

电化学合成聚吡咯（PPy）时,聚合电解液的pH 值对PPy 薄膜的形貌和性质有较大的影响,进而影响PPy薄膜对I^-/I₃^-的电催化活性以及基于PPy对电极（CE）的染料敏化太阳电池（DSSCs）的光电转换性能. 本文采用电化学恒电位方法,在掺杂氟的SnO₂（FTO）导电玻璃上合成出了对甲苯磺酸根离子掺杂的聚吡咯（PPy-TsO）电极,并将其作为DSSCs 的对电极. 通过改变吡咯聚合时聚合电解液的pH值,借助扫描电镜（SEM）、紫外-可见（UV-Vis）吸收光谱、X-射线光电子能谱（XPS）和循环伏安（CV）等表征技术,详细探讨了聚合溶液pH值对PPy CE形貌、结构及其对I^-/I₃^-的电催化性能的影响. 研究发现在pH 2.0下合成的聚吡咯对阴离子掺杂率最高且链共轭性最佳,具有对I^-/I₃^-氧化还原介质最强的催化能力,基于此PPy CE的电池光电转化效率也最高.pH 值太大或太小都不利于生成具有高掺杂率和高催化活性的PPy电极,组装成DSSCs后的光电转换效率也较低.     

Structure and electrochemical properties of magnetite and polypyrrole nanocomposites formed by pyrrole oxidation with magnetite nanoparticles

Nanocomposite of magnetic Fe₃O₄ nanoparticles and polypyrrole was prepared under sonication by a new chemical polymerization method during which Fe₃O₄ nanoparticles acted both as a pyrrole oxidant and as a component in the composite material. Synthesis of this nanocomposite was carried out in aqueous solution acidified to pH 2, a prerequisite for the formation of these types of material and to facilitate pyrrole oxidation by Fe₃O₄ nanoparticles. In this way, two kind of materials were produced: Fe₃O₄/PPy nanocomposite in which magnetite nanoparticles were dispersed in PPy matrix and Fe₃O₄-aggregates@PPy nanocomposite that exhibits structure in which aggregates of magnetite nanoparticles are surrounded by a layer of polymeric phase. In the latter case, the polymerization process took place in the presence of a surfactant. These nanocomposites were characterized by electron microscopy techniques, IR spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy and thermogravimetry. Particular attention was focused on the study of the electrochemical properties of the formed composites. The composite of Fe₃O₄ and PPy exhibits reversible electrochemical behaviour upon oxidation. The electrode process of the polymeric component oxidation in organic solvents such as acetonitrile and dichloromethane is very similar to the process in an aqueous solution.

     

Oxidation of a PPy-modified tantalum electrode

A tantalum electrode on which polypyrrole (PPy) had been previously formed by electropolymerization was galvanostatically electrolyzed in an aqueous solution of 0.01 wt% phosphoric acid. This process contains the irreversible oxidation of a PPy film, the decomposition of solvent, and the formation of Ta₂O₅ by the reaction of OH^? coming through the PPy film, with Ta electrodes. A three layer-structure (PPy/Ta₂O₅/Ta) was confirmed by electron spectroscopy for chemical analysis (ESCA). A PPy film containing CIO₄^? as dopant [PPy(CIO₄^?)] was significantly deteriorated in comparison with PPy(TsO^?) at the electrolysis. Therefore, the (PPy(TsO^?)/Ta₂O₅/Ta) system showed better electrical characteristics as a capacitor than the (PPy(CIO₄^?)/Ta₂O₅/Ta) system showed better electrical characteristics as a capacitor than the (PPy(ClO₄^?)/Ta₂O₅/Ta) system.     

氧化石墨烯/聚吡咯插层复合材料的制备和电化学电容性能

以FeCl₃-甲基橙(MO)为模板, 通过化学原位聚合法成功制备出氧化石墨烯/聚吡咯(GO/PPy)插层复合材料. 采用X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、扫描电镜(SEM)和透射电镜(TEM)等测试技术对复合材料进行物性表征. 此外, 利用循环伏安、恒电流充放电和交流阻抗测试方法对复合材料在两种不同水系电解液(1 mol·L^-1 Na₂SO₄和1 mol·L^-1 H₂SO₄)中的电化学性能进行了研究. 结果显示: 氧化石墨烯和聚吡咯表现出各自优势并发挥协同作用, 使得GO/PPy插层复合材料在中性和酸性电解液中都显示出可观的比电容. 电流密度为0.5 A·g^-1时, GO/PPy 插层复合材料在Na₂SO₄和H₂SO₄电解液中的比电容分别为449.1 和619.0 F·g^-1, 明显高于纯PPy的比电容. 经过800 次循环稳定性测试后, 两种不同电解液中, 复合材料初始容量的保持率分别为92%和62%. 其中酸性电解液体系中初始容量更大, 而中性溶液中具有更稳定的循环性能.     

Polypyrrole/γ-Fe2O3 magnetic nanocomposites synthesized in supercritical fluid

Polypyrrole/iron oxide (PPy/γ-Fe₂O₃) nanocomposites were synthesized by in situ oxidative polymerization of pyrrole in the presence of surface modified γ-Fe₂O₃ in supercritical carbon dioxide (scCO₂). The structural properties of nanocomposite particles thus obtained were characterized by FT-IR, thermal analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). It was found that ca. 50 nm γ-Fe₂O₃ nanoparticles were well dispersed in PPy powder in TEM pictures. X-ray photoelectron spectroscopy (XPS) analysis also support that all γ-Fe₂O₃ nanoparticles are encapsulated by PPy. Magnetic property of the nanocomposites was measured by SQUID, which indicated that the nanocomposites are superparamagnetic. The effects of different loadings of γ-Fe2O3 on the polymerization were also investigated.     

Facile and scalable fabrication of graphene/polypyrrole/MnO<Subscript>x</Subscript>/Cu(OH)<Subscript>2</Subscript> composite for high-performance supercapacitors

In this study, to improve the specific capacitance of graphene-based supercapacitor, novel quadri composite of G/PPy/MnO_x/Cu(OH)₂ was synthesized by using a facile and inexpensive route. First, a two-step method consisting of thermal decomposition and in situ oxidative polymerization was employed to fabricate graphene/polypyrrole/manganese oxide composites. Second, Cu(OH)₂ nanowires were deposited on Cu foil. Afterwards, for the electrochemical measurements, composite powders were deposited on Cu(OH)₂/Cu foil substrate as working electrodes. The synthesized samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy, and Raman spectroscopy. The XRD analysis revealed the formation of PPy/graphene, Mn₃O₄/graphene, and graphene/polypyrrole/MnO_x. In addition, the presence of polypyrrole and manganese oxides was confirmed using FT-IR and Raman spectroscopies. Graphene/polypyrrole/MnO_x/Cu(OH)₂ electrode showed the best electrochemical performance and exhibited the largest specific capacitance of approximately 370 F/g at the scan rate of 10 mV/s in 6 M KOH electrolyte. In addition, other electrochemical measurements (charge–discharge, EIS and cyclical performance) of the G/Cu(OH)₂, G/PPy/Cu(OH)₂, G/Mn₃O₄/Cu(OH)₂, and G/PPy/MnO_x/Cu(OH)₂ electrodes suggested that the G/PPy/MnO_x/Cu(OH)₂ composite electrode is promising materials for supercapacitor application.     

Conductive Composite Materials of Polyethylene and Polypyrrole with High Modulus and High Strength

Composite films of polyethylene (PE) and polypyrrole (PPy) were prepared by polymerization of PPy on an ultradrawn polyethylene film with high modulus and high strength in ferric chloride (FeCl₃) aqueous solution. The electrical conductivity of the composite film was found to be related to the polymerization conditions, such as polymerization temperature, polymerization time, the concentration and the oxidation potential of the FeCl₃ solution. Scanning electron microscopy, FTIR and ¹³C NMR spectra were used to elucidate the morphological and structural variations of PPy prepared under different conditions, which lead to the differences in the electrical properties of the resultant composite films. The best electrical conductivity of the composite was about 5.5 S/cm for the film prepared under optimum conditions. The Young's modulus and the tensile strength reached 80 GPa and 3.2 GPa, respectively, which indicated the successful production of a conductive polymer with high strength and high modulus.     

In situ polymerization and morphology of polypyrrole obtained in water‐soluble polymer templates

Several water‐soluble polymers were used as templates for the in situ polymerization of pyrrole to determine their effect on the generation of nanosized polypyrrole (PPy) particles. The polymers used include: polyvinyl alcohol (PVA), polyethylene oxide (PEO), poly(vinyl butyral), polystyrene sulfonic acid, poly(ethylene‐alt‐maleic anhydride) (PEMA), poly(octadecene‐alt‐maleic anhydride), poly(N‐vinyl pyrrolidone), poly(vinyl butyral‐co‐vinyl alcohol‐co‐vinyl acetate), poly(N‐isopropyl acrylamide), poly(ethylene oxide‐block‐propylene oxide), hydroxypropyl methyl cellulose, and guar gum. The oxidative polymerization of pyrrole was carried out with FeCl₃ as an oxidant. The morphology of PPy particles obtained after drying the resulting aqueous dispersions was examined by optical microscopy, and selected samples were further analyzed via atomic force microscopy. Among the template polymers, PVA was the most efficient in generating stable dispersions of PPy nanospheres in water, followed by PEO and PEMA. The average size of PPy nanospheres was in the range of 160 nm and found to depend on the molecular weight and concentration of PVA. Model reactions and kinetics of the polymerization reaction of pyrrole in PVA were carried out by hydrogen ¹H NMR spectroscopy using ammonium persulfate as an oxidant. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and Characterization of Polyvinylferrocene/Polypyrrole Composites

Conducting polymer composites of polyvinylferrocene and polypyrrole (PVF/PPy) were synthesized chemically by the in situ polymerization of pyrrole in the presence of PVF using FeCl₃ as oxidant. Acetic (CH₃COOH) and boric (H₃BO₃) acids were used as the synthesis medium. Effects of the synthesis medium on the properties of the PVF/PPy composite were investigated. The PVF/PPy composites and homopolymers were characterized by fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and magnetic susceptibility techniques. Conductivity measurements were performed using the four‐probe technique. We found that the conductivities of PVF/PPy‐H₃BO₃ (1.19 S cm^?1) and PVF/PPy‐CH₃COOH (4.5×10^?1 S cm^?1) increased relative to those of the homopolymers of PPy‐H₃BO₃ (2.1×10^?2 S cm^?1) and PPy‐CH₃COOH (1.2×10^?2 S cm^?1) due to the interaction of PVF with the pyrrole moiety. The stability of all homopolymers and composites were investigated by thermogravimetric analysis and by conductivity measurements during heating‐cooling cycles. There was a small drop in conductivity caused by the annealing of PVF/PPy composites at 70°C. The conductivity of all samples increased with temperature and exhibited stable electrical behavior with increasing temperature. TGA analysis of samples showed that the composites were more stable than the homopolymers or PVF separately. The magnetic susceptibility values of samples were negative, except for PVF/PPy‐H₃BO₃. Morphology changes of the composites investigated by scanning electron microscopy (SEM), attributed to synthesis conditions, have a significant effect on their conductivity.     

离子液体中吡咯的电化学聚合及性质研究

以1-丁基-3-甲基咪唑六氟磷酸盐离子液体作为溶剂和支持电解质,分别在铂电极和导电玻璃电极上电化学聚合得到了聚吡咯,聚合过程中发现,在离子液体中聚合的循环伏安图,其电流的变化和传统有机溶剂中的不同,通过交流阻抗技术研究了修饰电极的电化学性质,采用在线紫外、拉曼、红外谱对聚吡咯进行了光谱表征,得到了聚吡咯的特征峰,采用扫描电镜研究了聚合物的形貌。最后将修饰电极应用到了对对苯二酚的催化反应当中,显示了一定的催化作用。     

Electrochemical properties of LiFePO4/C synthesized using polypyrrole as carbon source

LiFePO₄/C composites were synthesized by pyrolysis of LiFePO₄/polypyrrole (PPy), which was obtained by an in situ chemical polymerization involving pyrrole monomer and hydrothermal synthesis LiFePO₄. All samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, cyclic voltammetry, and galvanostatic charge–discharge techniques. The results showed the LiFePO₄/C sintered at 800 °C containing 2.8 wt.% carbon exhibited a higher discharge capacity of 49.6 mAh·g⁻¹ at 0.1 C, and bare LiFePO₄ only delivered 11.6 mAh·g⁻¹ in 2 M LiNO₃ aqueous electrolyte. The possible reason for the improvement of electrochemical performance was discussed and could be attributed to the formation of aromatic compounds during the carbonization of PPy.     

Nanostructured ternary composites of PPy/CNT/NiFe2O4 and PPy/CNT/CoFe2O4: Delineating and improving microwave absorption

Two different ternary nanocomposites, PPy/CNT/CoFe₂O₄ and PPy/CNT/NiFe₂O₄, were synthesized by in situ polymerization method. The resulting composites were characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. They were evaluated with the aim of investigating microwave absorption properties. The results showed that the value of microwave reflection decreases as that of prepared nanocomposites increases. This happens with increase in the PPy content and polymerization on the surface.     

Preparation of NiAl double hydroxide@polypyrrole materials for high‐performance supercapacitors

A novel NiAl double hydroxide@polypyrrole (LDH@PPy) core–shell material was designed and fabricated by a facile in situ oxidative polymerization of pyrrole (Py) monomer. The microstructure and morphology of the LDH@PPy composites were determined by X‐ray diffractometer, Fourier transform infrared (FTIR), scanning electron microscopy/transmission electron microscopy, and thermogravimetric and differential thermal, revealing that the polypyrrole (PPy) was successfully coated onto the surface of the NiAl‐LDH (LDH) core and the loading amount of PPy impacted the thickness and the dispersion of the conductive PPy shell. The electrochemical performances of the LDH@PPy composites were also evaluated by cyclic voltammogram, electrochemical impedance spectroscopy, and galvanostatic charge–discharge measurements. The results indicated that the supercapacitor performances were attributed to the synergy of unique core–shell heterostructure and each individual component, where the LDH core provided the high‐energy storage capacity and the PPy shell with networks had high electronic conductivity. These shorted the ion diffusion pathway and made electrolyte ions more easily accessible for faradic reactions to enhance the electrochemical performance of the LDH@PPy composites. It was found that the LDH@PPy composite (LDH@PPy₇) fabricated at 7 mL?L^?1 of Py monomer feed exhibiting the best electrochemical performances with high specific capacitance of 437.5 F?g^?1 at 2 A?g^?1 and excellent capacitance retention of about 91% after 1000 cycles. The work provides a simple approach for designing organic–inorganic core–shell materials with potential application in supercapacitors. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1653–1662     

原位包覆导电聚吡咯的Li1.26Fe0.22Mn0.52O2富锂铁锰基正极材料的制备及电化学性能的提高

采用化学氧化聚合的方法成功合成了导电聚吡咯(PPy)包覆的纳米尺寸Li_1.26Fe_0.22Mn_0.52O₂(LFMO)正极材料。通过X射线衍射(XRD)检测样品的晶体结构,并通过扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察材料形态和微观结构。元素映射和傅里叶变换红外光谱结果表明,PPy导电网络存在于复合材料中,并且PPy均匀分布在LFMO颗粒上。通过恒流充放电测试和电化学阻抗谱(EIS)分析研究了所有样品的电化学性能,结果表明表面上的PPy显著降低了LFMO的电荷转移电阻。包覆PPy质量分数为2%的LFMO-2%PPy表现出极好的倍率性能和良好的循环稳定性,其在1C倍率下首次放电容量为206 mAh·g^-1,首圈库仑效率为87%,在1C和2C分别循环50圈后,其容量分别稳定在131和139 mAh·g^-1。     

In situ intercalative polymerization of conducting polypyrrole/montmorillonite nanocomposites

Conducting polypyrrole (PPy)‐montmorillonite (MMT) clay nanocomposites have been synthesized by the in situ intercalative polymerization method. The PPy‐MMT nanocomposites are characterized by field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, thermogravimetric analysis (TGA), and Fourier‐transform infrared (FTIR) spectroscopy. XRD patterns show that after polymerization by the in situ intercalative method with ammonium persulfate and 1 M HCl, an increase in the basal spacing from 1.2 to 1.9 nm was observed, signifying that PPy is synthesized between the interlayer spaces of MMT. TEM and SEM micrographs suggest that the coexistence of intercalated MMT layers with the PPy macromolecules. FTIR reveals that there might be possible interfacial interactions present between the MMT clay and PPy matrix. The study also shows that the introduction of MMT clay results in thermal stability improvement of the PPy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2279–2285, 2008     

Effect of Electrolytes on Redox Reactivity of Polypyrrole

Doping and dedoping characteristics of polypyrrole (PPy) formed electrochemically have been examined by means of energy-dispersive X-ray spectroscopy (EDS). Dodecylsulfate ions (DS⁻) and perchlorate ions (ClO⁻₄) were embedded simultaneously in PPy when both ions were present on the polymerization of pyrrole. Sequential formation of PPy in the single dopant system allowed PPy/ClO₄ to grow in the bulk of PPy/DS but not vice versa. DS⁻ was embedded not to leave the polymer on reduction but ClO⁻₄ moved in and out of the polymer on redox reaction. Cyclic voltammetry was employed to determine the redox reactivity of PPy in different electrolyte systems. NaClO₄ was a better electrolyte for cyclic redox reaction than LiClO₄ or KClO₄. NaCl was a good electrolyte for cyclic redox reaction but Cl⁻ failed to penetrate in the PPy/DS bulk on reoxidation. The cyclic redox reactivity lasted longest when PPy/DS was redox-cycled sequentially in the NaCl electrolyte system and then in the NaClO₄ system. © 1997 John Wiley & Sons, Ltd.     

Synthesis and characterization of polypyrrole nanofibers with different dopants

Nanostructures of polypyrrole (PPy) were synthesized in the presence of different dopants including hydrochloric acid (HCl), ferric chloride (FeCl₃), p‐toluene sulfonic acid (p‐TSA), camphor sulfonic acid (CSA), and polystyrene sulfonic acid (PSSA), using a simple interfacial oxidative polymerization method. The method is a reliable non‐template approach with relatively simple instrumentation, ease of synthesis, and economic viability for synthesizing PPy nanostructures. Morphology of synthesized PPy structures was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which indicate the formation of one‐dimensional (1D) nanofibers with average diameter of 75–180 nm. Energy dispersive spectrum (EDS) of the PPy nanofibers indicates the attachment of the dopants to the PPy backbone; the fact is further confirmed by the Fourier transform infrared (FTIR) spectra of PPy nanostructures. Thermal stabilities of the nanostructures explored using thermal gravimetric analysis (TGA) follow the order PPy‐p‐TSA > CSA > HCl > FeCl₃ > PSSA. It is noticed that the electrical conductivity (EC) of PPy nanostructures depends upon the nature of dopant (PPy‐p‐TSA > CSA > HCl > FeCl₃ > PSSA), PPy‐p‐TSA nanofibers showing the highest EC of 6 × 10^?2 Scm^?1. Copyright © 2009 John Wiley & Sons, Ltd.     

Improved lithium exchange at LiFePO4 cathode particles by coating with composite polypyrrole–polyethylene glycol layers

The polypyrrole–LiFePO₄ composites were synthesized by simple chemical oxidative polymerization of pyrrole (Py) monomer directly on the surface of LiFePO₄ particles. Properties of resulting polypyrrole–LiFePO₄ (PPy-LiFePO₄) samples (especially conductivity) are strongly affected by the preparation technique, polymer additives, and conditions during synthesis. For increasing of PPy-LiFePO₄ conductivity, we used polyethylene glycol (PEG) as additive during polymerization. The electrochemical behavior of the samples was examined by cyclic voltammetry and electrochemical impedance spectroscopy. It was found that PPy/PEG composite polymer decreased the particle to particle contact resistance. Impedance measurements showed that the coating of PPy/PEG significantly decreases the charge transfer resistance of LiFePO₄ electrodes.     

Facilely prepared polypyrrole-graphene oxide-sodium dodecylbenzene sulfonate nanocomposites by in situ emulsion polymerization for high-performance supercapacitor electrodes

The layered polypyrrole-graphene oxide-sodium dodecylbenzene sulfonate (PPyGO-SDBS) nanocomposites were facilely fabricated via an in situ emulsion polymerization method with the assistance of SDBS as dopant and stabilizer. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and electrochemical performance were employed to analyze the structure and the characteristics of the composites. The results showed that SDBS played an important role in improving the electrochemical performance of the PPyGO-SDBS, by dispersing the PPy between the layers of the GO. The obtained PPyGO-SDBS exhibited remarkable performance as an electrode material for supercapacitors, with a specific capacitance as high as 483 F g^?1 at a current density of 0.2 A g^?1 when the mass ratio of pyrrole to GO was 80:20. The attenuation of the specific capacitance was less than 20 % after 1,000 charge–discharge processes, supporting the idea that PPy inserted successfully into the GO interlayers. The excellent electrochemical performance seemed to arise from the synergistic effect between the PPy and the GO and the dispersion of the PPy induced by SDBS.     

Organic–inorganic polypyrrole‐surface modified SiO2 hybrid nanocomposites: a facile and green synthetic approach

Organic–inorganic hybrid nanocomposites composed of conductive polypyrrole (PPy) and surface modified silica (SiO₂) were successfully prepared through an in situ chemical oxidative polymerization in supercritical carbon dioxide (scCO₂). SiO₂ nanoparticles were surface modified using 3‐methacryloxypropyltrimethoxysilane (MPTMS) in order to disperse well in the medium. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the SiO₂ nanoparticles were encapsulated into the polymer. UV‐visible spectra of the diluted colloidal dispersions of PPy/SiO₂ hybrid nanocomposites were similar to those of PPy system. Fourier transform infrared spectroscopy (FT‐IR) suggested the strong interaction between PPy and SiO₂. Surface characterizations of nanocomposites were described by X‐ray photoelectron spectroscopy (XPS). The nanocomposites synthesized in scCO₂ have been shown to possess higher electrical conductivity and thermal stability. Copyright © 2009 John Wiley & Sons, Ltd.