Electroreductive polymerization of trans-[RuCl 2(vpy) 4] on Nd-Fe-B magnets: electrochemical impedance spectroscopy interpretation, Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy analysis

The electropolymerization of trans-[RuCl₂(vpy)₄] (vpy=4-vinylpyridine) monomer on Nd-Fe-B magnets was studied by electrochemical impedance spectroscopy (EIS). Impedance diagrams obtained during the polymerization process were used to monitor film formation. The EIS results gave insight into the electrochemical phenomena occurring at the magnet surface as the polymerization process progressed. The film structure and morphology were also studied by X-ray photoelectron spectroscopy, scanning electron microscopy and Raman spectroscopy. The Raman spectroscopy results showed that the polymerization takes place at the vinyl groups of the monomer and also that the redox polymer structure is very similar to that of the monomer. The ratio of the intensity of the XPS peaks for fluorine (from the electrolyte PF₆ ^–) and ruthenium present in the film showed that the polymer on Nd-Fe-B contained an equal proportion of Ru²⁺ and Ru³⁺, indicating that part of the film is positively charged, i.e. {[RuCl₂(vpy)₄]⁺} _n .     

A comparative study on the viscoelasticity and morphology of polyaniline films galvanostatically grown on bare and 4-aminothiophenol-modified gold electrodes using an electrochemical quartz crystal impedance system and SEM.

The equivalent-circuit parameters of the 9-MHz piezoelectric quartz crystal (PQC) resonance were measured in situ during the galvanostatic polymerization of aniline on 4-aminothiophenol(4-ATP)-modified and bare Au electrodes for ca. 2000 s, respectively. Two polymerization media, 0.100 mol L-1 aniline in 1.0 mol L-1 H2SO4 and in 2.0 mol L-1 HClO4 aqueous solutions, and two values of the current density, 12 and 36 microA cm-2, were used. At identical levels of the resonant frequency shifts in the solutions, obviously greater increases in the motional resistance (R1) were found after aniline polymerization on bare Au electrodes, though the absolute values of delta f0/delta R1 were all large; also, the resonant frequency shifts in air (delta f0g) were considerably smaller for PANI films grown on bare Au electrodes. It is thus concluded that, under identical polymerization conditions, (1) the PANI film grown on a bare gold electrode is rougher, less compact, and can entrap solution more notably; (2) the deposition efficiency of PANI is higher on a 4-ATP-modified Au electrode, owing to a significantly greater observed "dry" frequency shift, and thus a greater "net" mass value of the polyaniline backbone. SEM observations have confirmed that PANI films on 4-ATP-modified Au electrodes were smoother and more compact than those grown on bare Au ones under identical polymerization conditions. In addition, a technique of simultaneous measurements of the electroacoustic admittance of the PQC resonance and the electrochemical impedance was used to monitor the adsorption of 4-ATP onto a PQC gold electrode.     

Nanostructured polyaniline-coated anode for improving microbial fuel cell power output

An approach for improving the power generation of a dual-chamber microbial fuel cell by using a nanostructured polyaniline (PANI)-modified glassy carbon anode was investigated. Modification of the glassy carbon anode was achieved by the electrochemical polymerisation of aniline in 1 M H₂SO₄ solution. The MFC reactor showed power densities of 0.082 mW cm^?2 and 0.031 mW cm^?2 for the nano- and microstructured PANI anode, respectively. The results from electron microscopy scanning confirmed formation of the nanostructured PANI film on the anode surface and the results from electrochemical experiments confirmed that the electrochemical activity of the anode was significantly enhanced after modification by nanostructured PANI. Electrochemical impedance spectroscopic results proved that the charge transfer would be facilitated after anode modification with nanostructured PANI.     

Facile synthesis of polyaniline/TiO2/graphene oxide composite for high performance supercapacitors

The polyaniline/TiO₂/graphene oxide (PANI/TiO₂/GO) composite, as a novel supercapacitor material, is synthesized by in situ hydrolyzation of tetrabutyl titanate and polymerization of aniline monomer in the presence of graphene oxide. The morphology, composition and structure of the composites as-obtained are characterized by SEM, TEM, XRD and TGA. The electrochemical property and impedance of the composites are studied by cyclic voltammetry and Nyquist plot, respectively. The results show that the introduction of the GO and TiO₂ enhanced the electrode conductivity and stability, and then improved the supercapacitive behavior of PANI/TiO₂/GO composite. Significantly, the electrochemical measurement results show that the PANI/TiO₂/GO composite has a high specific capacitance (1020 F g⁻¹ at 2 mV s⁻¹, 430 F g⁻¹ at 1 A g⁻¹) and long cycle life (over 1000 times).     

Photoluminescence and Raman spectroscopy studies on polyaniline/PbI2 composite

Functionalization of PbI₂ with conjugated polymers (polyaniline-emeraldine base (PANI-EB) or polyaniline-emeraldine salt (PANI-ES)) is demonstrated by Raman and luminescence studies. PbI₂/PANI hybrid material was prepared by electrochemical polymerization of aniline onto the PbI₂ modified Pt electrode and mechanico-chemical reaction between the two constituents. PANI interacting with the PbI₂ gives rise to new Raman bands at 80, 144 and 170 cm⁻¹. First line reveals the formation of “stacking faults” that disrupt the I-Pb-I layers stacking along the c axis by the insertion of polymer molecules. The bands at 144 and 170 cm⁻¹ are attributed to the vibrational mode associated with Pb-NHR″₂ (R″=C₆H₄) bond. The functionalization of PbI₂ with PANI-EB brings forth the PANI-ES form. Depending on the semiconducting (PANI-EB) or conducting (PANI-ES) properties of the polymer in the PbI₂/PANI intercalated material, a partial or total collection of the charges generated under band to band irradiation is revealed by photoluminescence studies.     

Electrochemical nanogravimetric study on the ruthenium(III) trichloride–polyaniline nanocomposite

Ruthenium(III) trichloride microcrystals were soaked in aniline and aniline/acetonitrile mixtures. In all cases, polyaniline (PANI) was formed as a result of the intercalation of aniline into the layered structure of RuCl₃ crystal and the reaction between aniline and the host material. The appearance of polyaniline was proven by infrared spectroscopy. The as-formed (PANI) _x ^z+(RuCl₃) _y ^z− nanocomposites were attached to gold surfaces and studied by cyclic electrochemical nanogravimetry. The sorption of aniline and its effect on the nanocomposites immobilized on gold were also studied in supporting electrolytes. The redox behaviour of the composite shows the electrochemical transformations of both polyaniline and RuCl₃. The redox waves of PANI are similar to those observed for very thin PANI films. It attests that the response is originated from monolayer-like PANI film situated between RuCl₃ layers. The transport of the charge-compensating ions reflects the variation of the oxidation states of both PANI and RuCl₃. The nanocomposites behave as self-doped layers in the potential region when both constituents are charged, i.e. PANI is partially oxidized while RuCl₃ is partially reduced, since the electroneutrality is assured by mutual charge compensation. When PANI is reduced, cations enter the layer to counterbalance the negative charge resulting from the reduction of Ru(III) to Ru(II). It was also found that the intercalation of water molecules is—albeit still substantial—smaller than that of pure RuCl₃ microcrystals, which is related to the presence of PANI between the RuCl₃ layers. Dedicated to Prof. Mikhail A. Vorotyntsev on the occasion of his 60th birthday     

Polyaniline–DNA microsphere formation by simple electropolymerization

Polyaniline (PANI) microspheres were prepared by electrochemical polymerization. To obtain PANI having novel micro- and nanostructures, by the potential scan technique, aniline was electropolymerized in the presence of DNA using four polymerizing solutions containing different acids: H₂SO₄, C₆H₅SO₃H, HClO₄, and CF₃COOH. The growth rate of the PANI film on the electrode surface decreased by the presence of DNA, suggesting that DNA interacted with the growing PANI molecules during the electropolymerization. The growth rate also depended on the type of acid, i.e., the anion, in the polymerizing solution and was in the order of SO₄ ²⁻ > C₆H₅SO₃ ⁻ > ClO₄ ⁻ > CF₃COO⁻, which significantly coincided with the reverse order of the Hofmeister series representing the lyophilicity of the anion. When aniline was electropolymerized in the CF₃COOH polymerizing solution containing DNA, PANI microspheres were obtained without any templates. This PANI showed a sufficient redox activity in the less acidic solution in which the ordinary PANI has a slight redox activity. On the other hand, the electronic state of the PANI differed from the ordinary ones; a new absorption band was evident at 620 nm. The difference in the redox activity and electronic state suggested that the DNA molecules were incorporated in the PANI and electronically interacted with the PANI molecules.     

Synthesis,Structural Characterization,and Electrochemical Properties of Isotruxene–Polyaniline Hybrid Systems

The synthesis, structural characterization, and electrochemical properties of a series of isotruxene–polyaniline (PANI ) hybrid systems (SITPs , SITAs , and CITs ) are reported. The syntheses were performed by in situ chemical oxidative polymerization of aniline in the presence of isotruxene additives ITP and/or ITA at specific aniline‐to‐additive molar ratios. The polymers SITPs and SITAs display granular morphology, but for the polymers CITs a spherical morphology with a diameter of 300–500 nm is found. These hybrid systems display electrochemical capacitive performance superior to those of the parent PANI prepared under the same condition (e.g., 385–463 vs. 181 F/g at 3 mA /cm² current density during charge–discharge test). Molecular (star‐shaped or hyperbranched vs. linear topology) and supramolecular (isotruxene–PANI π–π and cation–π interactions) models in accounting for the observed morphology and electrochemical properties are provided.     

纳米纤维聚苯胺膜在不锈钢电极表面的生长过程

研究了脉冲电流法(PGM)聚合苯胺时, 纳米纤维聚苯胺(PANI)膜在不锈钢(SS)电极表面的生长过程. 用计时电位法和扫描电子显微镜(SEM)表征了聚苯胺生长过程的电化学特征和微观形貌; 并通过循环伏安(CV)法研究了苯胺的聚合速率. 结果表明, 聚苯胺的生长经历了两个阶段, 首先是在裸不锈钢电极表面上形成颗粒状聚苯胺, 此时聚合电位约为1.10 V, 经历了30 s后, 电极表面被一层颗粒状聚苯胺膜所覆盖; 在此基础上, 聚苯胺以纳米纤维状结构继续生长, 当颗粒状聚苯胺被纳米纤维状聚苯胺膜完全覆盖时, 聚合电位降至0.75 V左右并保持稳定.     

Electrochemical Sensor Based on Molecularly Imprinted Polymer Film Prepared with Functional Abietic‐Type Acids as Cross‐Linker for the Determination of Quinine

A novel cross‐linker (functional abietic‐type acids) for preparing highly sensitive, molecularly imprinted sensors was proposed for quinine determination. A MIP film was created on a glassy carbon electrode for determination of quinine using free radical polymerization method. The modification procedure was characterized via electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The interaction between functional monomer and target molecule was observed by UV spectrometric methods. Under the optimal experimental conditions, the peak currents were proportional to the concentrations of quinine in the range from 8.0×10^?7 to 2.6×10^?4 M with a detection limit of 2.0×10^?8 M. Meanwhile the prepared sensor showed sensitive and selective binding sites for quinine. Determination of quinine in tonic water showed good recovery.     

Fabrication of Polyaniline/Silver Nanocomposite Under Gamma-ray Irradiation

Polyaniline (PANI)/silver composite was one-step synthesized under γ-ray irradiation. The structure of the composite was characterized by Fourier transform infrared spectroscopy, UV-Visible, and X-ray diffraction, which indicated that PANI and face-centered-cubic silver were synthesized under γ-ray irradiation. The reaction mechanism were discussed, which revealed that the PANI was formed by the reaction of aniline cation radicals formed by the reaction of aniline cation and ·OH, and Ag was formed by the reaction of Ag⁺ and e^-_aq. The morphology of the composite consisted of PANI nanofibers and Ag nanoparticles, and the mechanism of the morphology formation was discussed, which revealed that the rapid mixing like polymerization process might play an important role. It was revealed that the transport behavior of the composite well fitted with the variable-range-hopping model in 80-300 K and deviated from the model below 80 K.     

Polyaniline encapsulated silicon nanocomposite as high-performance anode materials for lithium ion batteries

Polyaniline encapsulated silicon (Si/PANI) nanocomposite as anode materials for high-capacity lithium ion batteries has been prepared by an in situ chemical polymerization of aniline monomer in the suspension of Si nanoparticles. The obtained Si/PANI nanocomposite demonstrates a reversible specific capacity of 840 mAh g^?1 after 100 cycles at a rate of 100 mA g^?1 and excellent cycling stability. The enhanced electrochemical performance can be due to that the polyaniline (PANI) matrix offers a continuous electrically conductive network as well as enhances the compatibility of electrode materials and electrolyte as a result of suppressing volume stress of Si during cycles and preventing the agglomeration of Si nanoparticles.     

Electrochemical polymerization of polyaniline doped with Zn2+ as the electrode material for electrochemical supercapacitors

Polyaniline doped with Zn²⁺ (PANI/Zn²⁺) films was synthesized by cyclic voltammetric method on stainless steel mesh substrates in 0.2 mol L^?1 aniline and 0.5 mol L^?1 sulfuric acid electrolyte with various concentrations of zinc sulfate (ZnSO₄·7H₂O). The structure and morphology of PANI and PANI/Zn²⁺ films were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy techniques, respectively. The electrochemical properties of PANI and PANI/Zn²⁺ films were investigated by cyclic voltammetry, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy in 0.5 mol L^?1 H₂SO₄ electrolyte in a three-electrode system. The results show that the surface morphology of PANI/Zn²⁺ is more rough than that of pure PANI. The specific capacitance of the PANI/Zn²⁺ film displays a larger specific capacitance of 738 F g^?1, lower resistance, and better stability as compared with the pure PANI film. Thus, good capacitive performance demonstrates its potential superiority for supercapacitors.     

Electrochemical characterization of PANI-Nafion membranes and their electrocatalytic activity

PANI-Nafion^® membranes were prepared by a chemical method in which the faces of a commercial Nafion membrane were contacted with two acid solutions containing an oxidant (Fe³⁺) and aniline respectively. They were then characterized by a variety of electrochemical techniques (cyclic voltammetry, chronoamperometry, ac impedance). PANI was stored mostly in the vicinity of the Nafion face exposed to the oxidant. When this face was contacted with Hg and the other with electrolyte solutions, typical electrochemical responses of PANI were detected. Electrocatalytic reduction of O₂ and oxidation of N₂H₄ were achieved on PANI-Nafion electrodes and found to be only slightly slowed down with respect to ordinary PANI film electrodes, at variance with a fast process such as Fe³⁺ reduction, the rate of which was severely limited by diffusion through the membrane.     

The effect of the polyaniline morphology on the performance of polyaniline supercapacitors

The polyaniline (PANI) prepared by the pulse galvanostatic method (PGM) or the galvanostatic method on a stainless steel substrate from an aqueous solution of 0.5 mol/l H₂SO₄ with 0.2 mol/l aniline has been studied as an electroactive material in supercapacitors. The electrochemical performance of the PANI supercapacitor is characterized by cyclic voltammetry, a galvanostatic charge–discharge test and electrochemical impedance spectroscopy in NaClO₄ and HClO₄ mixed electrolyte. The results show that PANI films with different morphology and hence different capacitance are synthesized by controlling the synthesis methods and conditions. Owing to the double-layer capacitance and pseudocapacitance increase with increasing real surface area of PANI, the capacitive performances of PANI were enhanced with increasing real surface area of PANI. The highest capacitance is obtained for the PANI film with nanofibrous morphology. From charge–discharge studies of a nanofibrous PANI capacitor, a specific capacitance of 609 F/g and a specific energy density of 26.8 Wh/kg have been obtained at a discharge current density of 1.5 mA/cm². The PANI capacitor also shows little degradation of capacitance after 1,000 cycles. The effects of discharge current density and deposited charge of PANI on capacitance are investigated. The results indicate that the nanofibrous PANI prepared by the PGM is promising for supercapacitors.     

Electrocatalytic Dioxygen Reduction at Glassy Carbon Electrode Modified with Polyaniline Grafted Multiwall Carbon Nanotube Film

The work details the electrocatalysis of oxygen reduction reaction (ORR) in 0.5 M H₂SO₄ medium on a modified electrode containing a film of polyaniline (PANI) grafted multi‐wall carbon nanotube (MWNT) over the surface of glassy carbon electrode. We have fabricated a novel modified electrode in which conducting polymer is present as connected unit to MWNT. The GC/PANI‐g‐MWNT modified electrode (ME) is fabricated by electrochemical polymerization of a mixture of amine functionalized MWNT and aniline with GC as working electrode. Cyclic voltammetry and amperometry are used to demonstrate the electrocatalytic activity of the GC/PANI‐g‐MWNT‐ME. The GC/PANI‐g‐MWNT‐ME exhibits remarkable electrocatalytic activity for ORR. A more positive onset potential and higher catalytic current for ORR are striking features of GC/PANI‐g‐MWNT‐ME. Rapid and high sensitivity of GC/PANI‐g‐MWNT‐ME to ORR are evident from the higher rate constant (7.92×10² M^?1 s^?1) value for the reduction process. Double potential chronoamperometry and rotating disk and rotating ring‐disk electrode (RRDE) experiments are employed to investigate the kinetic parameters of ORR at this electrode. Results from RDE and RRDE voltammetry demonstrate the involvement of two electron transfer in oxygen reduction to form hydrogen peroxide in acidic media.     

Synthesis and characterization of C60/polyaniline composites from interfacial polymerization

C₆₀/polyaniline (PANI) nanocomposites have been synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in the presence of C₆₀ by using an interfacial reaction. When compared with the pure PANI nanofibers from the similar process, the diameter of the obtained C₆₀/PANI nanofibers was increased because of the encapsulation of C₆₀ into PANI during aniline polymerization, which resulted from the charge‐transfer interactions between C₆₀ and aniline fragment in PANI. In addition, the resulting C₆₀/PANI nanocomposites synthesized from the low initial C₆₀/aniline molar ratio (less than 1:25) showed the homogenous morphology composed of fiber network structures, which has an electrical conductivity as high as 1.1 × 10^?4 S/cm. However, the C₆₀/PANI nanocomposites from the higher initial C₆₀/aniline molar ratio (more than 1:15) showed the nonuniformly distributed morphology, and the electrical conductivity was decreased to 3.5 × 10^?5 S/cm. Moreover, the C₆₀/PANI nanocomposites from the interfacial reaction showed a higher value of electrical conductivity than the mechanically mixed C₆₀/PANI blends with the same C₆₀ content, because of the more evenly distributed microstructures. FTIR, UV–vis, and CV data confirmed the presence of C₆₀ and the significant charge‐transfer interactions in the resultant nanocomposites, which was responsible for the morphology development of the C₆₀/PANI and the variation of the electrical conductivity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Ternary Ag/Polyaniline/Au nanocomposites: Preparation,characterization and electrochemical properties

Ternary Ag/Polyaniline/Au nanocomposites were synthesized successfully by immobilizing of Au nanoparticles (NPs) on the surface of Ag/Polyaniline (PANI) nanocomposites. Ag/PANI nanocomposites were prepared via in situ chemical polymerization of aniline in the presence of 4-aminothiophenol (4-ATP) capped silver colloidal NPs. Then, uniform gold (Au) NPs were assembled on the surface of resulted Ag/PANI nanocomposites through electrostatic interaction to get Ag/Polyaniline/Au nanocomposites. The nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), ultraviolet visible spectroscopy (UV-Vis), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Moreover, Ag/PANI/Au nanocomposites were immobilized on the surface of a glassy carbon electrode and showed enhanced electrocatalytic activity for the reduction of H₂O₂ compared with Ag/PANI.     

Pseudo Capacitive Studies of Polyaniline-Carbon Nanotube Composites as Electrode Material for Supercapacitor

This study describes the formation of composites of polyaniline (PANI)-Carbon Nanotube (CNT) using in situ chemical oxidative polymerization of the monomer aniline. The PANI-CNT composites were characterized by FTIR and UV-Visible spectroscopy and XRD method. The surface morphology of the composites was characterized by scanning electron microscopy (SEM). Pseudo-capacitive behavior of deposited PANI over the surface of CNT was investigated by means of cyclic voltammetry. The composite was mixed with activated carbon for making the electrode. The specific capacitance of the prepared electrode was tested by means of a half cell test. The PANI-CNT composite with 0.02 M aniline in initial polymerization solution had the thinnest layer and highest specific capacitance of 597.82 F/g in 1 M H₂SO_4.     

层层自组装原位聚合聚苯胺复合膜成膜机理研究

从苯胺单体出发, 通过原位聚合、现场掺杂以及基于静电力的层层自组装制备了聚苯胺复合膜. 通过苯胺活性溶液的温度及颜色变化跟踪聚合反应进程, 同时考察不同聚合反应阶段所得聚苯胺复合膜的紫外-可见吸收, 并进一步探讨聚苯胺复合膜的成膜机理. 研究表明, 成膜机制是由聚合反应初始阶段的苯胺阳离子或苯胺阳离子自由基通过静电作用快速吸附到负电性的基片表面, 形成均匀的聚合中心, 链增长生成聚苯胺; 该聚苯胺在酸性条件下经现场掺杂显电正性, 可吸附电负性的聚苯乙烯磺酸钠(PSS), 以此循环层层组装得到多层聚苯胺复合膜.