Porous Polyaniline Research Articles

Hydrogels: Assembly of Viral Hydrogels for Three‐Dimensional Conducting Nanocomposites (Adv. Mater. 30/2014)

The cover image represents a bioengineered M13 virus (grey) that can be genetically programmed to bind pristine singlewalled nanotubes (SWNTs) (black) in a controlled fashion along the length of the virus homogeneously. These SWNTs–virus complexes are used as the basis for the formation of crosslinked hydrogel scaffolds for the design of 3D porous polyaniline nanostructures (green) which integrate SWNTs, as reported by P. T. Hammond, A. M. Belcher, and co-workers on page 5101. The templated assembly promises facile synthesis of 3D conducting nanocomposites for a myriad of applications, from sensing to energy conversion and energy storage.

Inexpensive synthesis route of porous polyaniline–ruthenium oxide composite for supercapacitor application

Abstract Porous polyaniline–ruthenium oxide composite has been synthesized using a successive ionic layer adsorption and reaction (SILAR) method. The result of X-ray diffraction indicates the amorphous nature of polyaniline–ruthenium oxide (PANI–RuO2) composite. Fourier transform infrared (FT-IR) and FT-Raman spectroscopy studies reveal the formation of composite material. The morphology of PANI–RuO2 composite observed using scanning electron microscope (SEM) shows hierarchical nanofibers with small particles grown on the nanofibers. The electrochemical measurement shows that PANI–RuO2 composite electrode material yields specific capacitance of 664 F/g and higher capacitance retention (89%) of its initial capacitance after 5000 cycles. The unique structure of PANI–RuO2 composite and the coexistence of conducting PANI with RuO2 are found to be responsible for the superior electrochemical properties.

A stable polyaniline-benzoquinone-hydroquinone supercapacitor.

A Polyaniline-Supercapacitor with quinone electrolytes remains stable over 50 000 galvanostatic charge-discharge cycles. The quinones provide superior stability by preventing the conversion of porous polyaniline to a highly reactive state. Our work shows that highly stable polymer-supercapacitors can be engineered by combining electrochemically active polymers and redox-active electrolytes with concerted electrochemical properties.

Flexible polymer electrode using self-assembled porous polyaniline

The soft portable electronic equipment, such as rollup displays and wearable devices, requires the development of flexible energy sources. Among them, a bendable battery needs soft electrode materials. Polyaniline (PANI) has been examined as an electrode material, on the basis of reversible doping behaviour, inexpensive cost, and low self-discharge rate. However, PANI has some shortcomings of poor processability and performance. Then in this study, self-assembled porous PANI electrode was prepared by emulsion polymerisation of aniline and polyvinyl alcohol (PVA). PVA was chosen as a supporting material to make porous structure and increases the flexibility. And the characterisations of the polymer electrode were carried out by means of 4-point probe, UV-vis spectra, scanning electron microscopy (SEM), and X-ray diffraction (XRD), etc. Also, the electric conductivity of self-assembled porous PANI electrode was intensively investigated.

Electrochemical synthesis of a microporous conductive polymer based on a metal-organic framework thin film.

A new approach to preparing 3D microporous conductive polymer has been demonstrated in the electrochemical synthesis of a porous polyaniline network with the utilization of a MOF thin film supported on a conducting substrate. The prepared porous polyaniline with well-defined uniform micropores of 0.84 nm exhibits a high BET surface area of 986 m(2) g(-1) and a high electric conductivity of 0.125 S cm(-1) when doped with I2, which is superior to existing porous conducting materials of porous MOFs, CMPs, and COFs.

Electrochemical Synthesis of a Microporous Conductive Polymer Based on a Metal–Organic Framework Thin Film

AbstractA new approach to preparing 3D microporous conductive polymer has been demonstrated in the electrochemical synthesis of a porous polyaniline network with the utilization of a MOF thin film supported on a conducting substrate. The prepared porous polyaniline with well‐defined uniform micropores of 0.84 nm exhibits a high BET surface area of 986 m2 g−1 and a high electric conductivity of 0.125 S cm−1 when doped with I2, which is superior to existing porous conducting materials of porous MOFs, CMPs, and COFs.

Facile growth of heparin-controlled porous polyaniline nanofiber networks and their application in supercapacitors

Herein, we present the synthesis of porous polyaniline (PANI) nanofiber networks by a chemical oxidative polymerization method using a biomolecule, heparin. Long uniform nanofibers were formed when the weight ratio of heparin to aniline was 0.25 (PANIH-0.25), where the average nanofiber diameter was about 80–110 nm. No such PANI nanofibers were formed at other weight ratios. A comparison of the morphology of PANIH-0.25 was made with the pure PANI which was synthesized without any template. We further studied the potential of PANIH-0.25 as a nanostructured electrode material for the supercapacitor applications. The PANIH-0.25 nanofiber electrode yielded a six-fold improvement in specific capacitance when compared with pure PANI. The PANIH-0.25 electrode exhibited a specific capacitance of 732.18 ± 24.1 F g−1 and a longer cycle life with the capacitance retention of 72.28% after 1000 cycles. The observed capacitance was elucidated and justified based on theoretical considerations.

Oriented ZnO nanorods grown on a porous polyaniline film as a novel coating for solid-phase microextraction

In this work, oriented ZnO nanorods (ZNRs) were in situ hydrothermally grown on a porous polyaniline (PANI) film to function as a solid-phase microextraction (SPME) coating. Scanning electron microscopy (SEM) study revealed that the majority of oriented ZNRs grew from pores of PANI matrix, which protected the ZNRs from easily peeling off during operation. Furthermore, in this process, a thin layer of PANI was found to cover the ZNRs, which can enlarge the effective surface area of the composite coating. This ZNRs/PANI composite coating combined the merits of both ZNRs and PANI and, thus, has several advantages over that of sole PANI film and ZNRs coating such as improved extraction efficiency for benzene homologues, enhanced mechanical stability and longer service life (over 150 cycles of SPME-GC operation). Coupled with gas chromatography-flame ionization detector (GC-FID), the optimized SPME-GC-FID method was used for the analysis of six benzene homologues in water samples. The calibration curves were linear from 1 to 1000μgL−1 for each analyte, and the limits of detection were between 0.001 and 0.024μgL−1. Single fiber repeatability and fiber-to-fiber reproducibility were in the range of 1.3–6.8% and 5.3–11.2%, respectively. The spiked recoveries at 100 and 5μgL−1 for three environmental water samples were in the range of 79.8–115.4% and 73.7–117.4%, respectively.

Ion diffusion and optical switching performance of 3D ordered nanostructured polyaniline films for advanced electrochemical/electrochromic devices

Nanostructured polyaniline (PANI) has the ability of fast and reversible acid/base doping/dedoping, multi-color changes and electron-donating/accepting using surface or near-surface reactions. Here we report PANI films with 3D ordered nanostructures through template-assisted electrodeposition method and aim to study the ion diffusion behavior as well as optical switching properties. It is found the ion diffusion coefficient is greatly increased because of the chain and crystalline structural modulation of deposited polyaniline arising from the template confinement effect. The ion diffusion reversibility and ion storage of 3D ordered macroporous (3DOM) PANI is highly improved due to the interconnected porous structure, which benefits for the fast penetration of ions. The optical switching properties of 3DOM PANI are also highly enhanced especially in the infrared region mainly because of the extended optical transmission path associated with the interconnected porous structure. The outstanding ion/electron doping/dedoping performance and better interaction with lights shown here render the ordered porous polyaniline a promising candidate as high-density electrochemical/electrochromic energy materials.

Preparation of Porous Hollow Polyaniline Microspheres and Study on Their <I>In Vitro</I> Release Behavior

We report the synthesis of porous hollow polyaniline (PANI) microspheres loaded with Acid Red 8 dye (200-600 nm diameters under different reaction conditions) by using spherically mesoporous aggregates of Fe3O4 particles as soft templates and ammonium persulfate (APS) as the oxidant at 2.5 degrees C. Since the as-prepared spherical aggregates of Fe3O4 particles are readily dissolved in acidic aqueous solution, these spherical aggregates can be treated as soft template for the fabrication of hollow spheres. This process is therefore more convenient than other reported methods which require the post-treatment to remove the templates under strict conditions. The influence of the synthetic conditions on the formation and size of PANI microspheres was investigated. The morphology was confirmed by transmission electron microscopy (TEM). The chemical and electronic structures of the PANI microspheres were also studied by FTIR and UV-Vis spectrometry, respectively. The experimental in vitro release showed that these porous hollow PANI microspheres provided a controlled release of the entrapped dye, which was regulated by pH. Furthermore, the releasing behavior was qualitatively explained based on effective dissociation constant as a function of the pH.

Porous polyaniline nanofiber/vanadium pentoxide layer-by-layer electrodes for energy storage

There has been long-standing interest in hybrid electrodes containing an electronically conductive polymer and an inorganic cathode material for electrochemical energy storage. Conductive polymers such as polyaniline serve to enhance the conductivity of the electrode, and are electrochemically active themselves. Here, we report the layer-by-layer (LbL) assembly of polyaniline (PANI) nanofibers and V2O5 to form hybrid electrodes for electrochemical energy storage. The resulting electrode is highly porous and significantly exceeds in performance relative to an analogous electrode assembled with conventional PANI in place of PANI nanofibers. By utilizing PANI nanofibers in place of conventional PANI, significant gains in capacity (3×), specific energy (40×), and specific power (4×) are realized. The growth of the film is investigated using profilometry and quartz crystal microbalance; the thickness of the film increases linearly with respect to the number of layer pairs deposited. It is found that the electrochemical response possesses contributions from both PANI nanofibers and V2O5, and that the electrochemical performance of this LbL system is dependent on film thickness. The electrode contains 59 wt% V2O5 and stores 0.8 mol Li+ per mol of V2O5. A film thickness of 1.2 μm yields optimum results, with a discharge capacity of 320 mA h g−1, a power density of 4000 mW g−1, and an energy density of 886 mW h g−1 (per mass of active cathode), depending on discharge current. After 100 cycles, the electrode retains 75% of its initial capacity, and no appreciable volumetric expansion after cycling is observed. These results highlight the promise of porous electrodes made via LbL assembly, where two dissimilar materials can be intimately blended to achieve synergistic properties.

Hierarchically porous hybrids of polyaniline nanoparticles anchored on reduced graphene oxide sheets as counter electrodes for dye-sensitized solar cells

Hierarchically porous polyaniline–reduced graphene oxide hybrids have been developed via oxidative polymerization of aniline by MnO2 on reduced graphene sheets under acidic conditions (named M-PANI@rGO). The formation mechanism of the above hybrids indicates that the MnO2 undergoes oxidative disintegration and results in the porous structure of polyaniline (PANI) nanoparticle formation on the reduced graphene oxide (rGO) surface. The scanning electron microscopy (SEM) images and Brunauer–Emmett–Teller (BET) nitrogen sorption–desorption measurement clearly showed the nanoporous nature of the M-PANI@rGO hybrids. TEM-EDX confirmed the complete removal/degradation of MnO2 during the oxidative polymerization of aniline. Just for comparison, PANI–rGO hybrids have also been prepared via conventional polymerization using (NH4)2S2O8 as the oxidant (named C-PANI@rGO). When these different architectural PANI@rGO hybrids were applied as the counter electrode for dye-sensitized solar cells (DSSCs), the short-circuit current density (Jsc) and power-conversion efficiency (η) of the DSSCs with C-PANI@rGO hybrids are measured to be 11.64 mA cm−2 and 5.62%, respectively, while the corresponding values are 12.88 mA cm−2 and 6.15% for the DSSCs with M-PANI@rGO hybrids, which is comparable to 6.73% for the cell with a Pt counter electrode under the same experimental conditions. The hierarchically porous M-PANI@rGO hybrid is thus a promising candidate to replace platinum as a counter electrode for DSSCs.

Synthesis and characterization of SnO2/polyaniline nanocomposites by sol–gel technique and microemulsion polymerization

Nanostructured SnO2 was prepared based on the sol–gel method. Aniline monomer was polymerized by microemulsion polymerization in the presence of nanocrystalline SnO2 to form inorganic–organic nanocomposite materials, in which SnO2 nanoparticles were embedded within porous polyaniline (PANI). Structural and morphological characterization of SnO2 and SnO2/PANI was carried out using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The XRD pattern suggested that PANI did not modify the crystal structure of SnO2. FT-IR spectrum proved that aniline was successfully composited with the nanostructured SnO2. TEM analysis showed that the SnO2 nanoparticles with a diameter of ca. 15nm were embedded well in the porous PANI. Conductivity analysis indicated that the SnO2/PANI nanocomposites had a higher conductivity than that of the pure SnO2 nanopowders.

Thermoelectric properties of porous multi-walled carbon nanotube/polyaniline core/shell nanocomposites

Porous polyaniline (PANI)-coated multi-walled carbon nanotube (MWNT) core/shell nanohybrids were fabricated through in situ polymerization and subsequently assembled into macroscopic composites. N2 adsorption/desorption analysis indicated that the volume of nanopores increased significantly, which could make a significant contribution to phonon scattering. Thermal annealing was also carried out to improve the Seebeck coefficient of the as-produced nanocomposites. The optimal sample showed electrical conductivity of 14.1 S cm−1, a Seebeck coefficient of 79.8 μV K−1 and thermal conductivity of 0.27 W mK−1, resulting in a highest figure of merit (ZT) of 0.01 at a very low loading of MWNTs (<1 wt%). These results will provide a potential direction to enhance thermoelectric performance of organic materials and also facilitate the application of organic materials in thermal energy harvesting or cooling.

Polyaniline porous counter-electrodes for high performance dye-sensitized solar cells

Porous polyaniline–camphorsulfonic acid (PANI–CSA) counter-electrodes (CEs) for dye-sensitized solar cells (DSSCs) were fabricated by secondary doping-based polymerization with different porogen decomposition. The average pore diameter was ca. 50 and 150 nm for BPO and AIBN, respectively. The increased Brunauer–Emmett–Teller (BET) surface area of porous PANI–CSA CEs facilitated facile electron exchange between the CEs and the redox electrolyte, resulting in higher electro-catalytic performance than that of Pt-coated indium-doped tin oxide (ITO) CE. The porous PANI–CSA nanostructures with increased BET surface area exhibited an equivalent incident photon-to-electron conversion efficiency (IPCE) of 68.86% and a power-conversion efficiency (PCE, η) of 6.23% compared to DSSCs containing Pt-coated ITO CE (IPCE of 68.70% and η = 6.17%). It is noteworthy that the performance of DSSCs with porous PANI–CSA CEs represented a 101.0% relative efficiency compared to Pt-coated CEs.

Capacitance behaviors of nanorod polyaniline films controllably synthesized by using a novel unipolar pulse electro-polymerization method

A novel unipolar pulse electro-polymerization (UPEP) method was used to prepare nanorod polyaniline (PANI) films on platinum substrates from aqueous solution containing 0.2 mol L −1 of aniline and 0.5 mol L −1 of sulphuric acid. The unipolar pulse waveform consisted of an applied anodic potential during the on-period and an open-circuit potential (zero current) during the off-period. The effects of pulse deposition parameters on the electrochemical properties of PANI films were investigated by potential cycling in 0.5 mol L −1 of H 2SO 4 solution. The supercapacitive performances of as-prepared PANI films were also investigated in the 0.5 mol L −1 of H 2SO 4 solution via charge/discharge tests as well as electrochemical impedance spectroscopy (EIS). The surface morphology and conformation of PANI films were characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy, respectively. Experimental results indicated that nanorod PANI films with uniform distribution on Pt were formed by using this novel method, and the anodic pulse potential should be the primary factor to influence the morphology and the conformation of PANI film. The PANI films prepared by UPEP method displayed much higher ion exchange capacity, better stability and more excellent supercapacitive performances than those by other methods such as the common cyclic voltammetric method (CVM) and potentiostatic method (PM). It should be attributed to the highly porous nano-sized PANI with short-fiber or rod-like structure and the depressed hydrolysis of aniline. The highest specific capacitance value of 907.9 F g −1 was obtained when the pulse potential, aniline concentration, pulse frequency and duty cycle were 0.85 V, 0.2 mol L −1, 1.25 s −1 and 50%, respectively.

MnO2 assisted oxidative polymerization of aniline on graphene sheets: Superior nanocomposite electrodes for electrochemical supercapacitors

Graphene-polyaniline nanocomposite electrodes have been developed via oxidative polymerization of aniline by MnO2 on a graphene surface for electrochemical supercapacitor applications. The formation mechanism of the above nanocomposite indicates that the MnO2 undergoes oxidative disintegration and results in porous polyaniline (PANI) nanofibers formation on the graphene surface. The electron microscopic (SEM and TEM) images clearly showed the presence of porous PANI nanofiber formation on the graphene-PANI nanocomposites. The XRD, SEM-EDX and TG analysis confirmed the complete removal/degradation of MnO2 during the oxidative polymerization of aniline. For comparison, graphene-PANI nanocomposites have also been prepared via conventional polymerization using (NH4)2S2O8 as oxidant in acidic medium and the effect of carbon nanotube (CNT) addition has been studied. The electrochemical properties of different graphene-PANI nanocomposites have been investigated using galvanostatic charge-discharge, cyclic voltammetry and electrochemical impedance spectroscopy measurements. A superior supercapacitive performance (∼15 to 40% more than the reported capacitance) has been observed for the graphene-PANI nanocomposite electrode obtained via oxidative polymerization of aniline by MnO2. Addition of CNT into the graphene-PANI nanocomposite prepared via the conventional polymerization method showed improved specific capacitance and stability. Carbon nanofibers and graphite have been used as the carbon source and the effect of the carbon source on the specific capacitance has been investigated.

Direct electrochemisty and electrocatalysis of anthraquinone-monosulfonate/polyaniline hybrid film synthesized by a novel electrochemical doping-dedoping-redoping method on pre-activated spectroscopically pure graphite surface

Polyaniline (PANI) film in the form of emeraldine salt (ES) doped with anthraquinone-2-sulfonate (AQS) was synthesized by a novel electrochemical doping-dedoping-redoping method on pre-activated spectroscopically pure graphite electrode surface. SEM showed the highly porous microstructure with sponge-like morphology of the AQS/PANI hybrid film, which has more available active sites for facilitating electron transfer and energy efficiency of redox reactions. FTIR and UV-vis spectra demonstrated the incorporation of AQS into the conductive PANI matrix. Cyclic voltammetric (CV), electrochemical impedance spectroscope (EIS), rotating ring-disk electrode (RRDE) and chronoamperometry (CA) techniques indicated that the AQS/PANI composite has high electrocatalytic activity and remarkable stability for the two-electron reduction of oxygen via an electrochemical-chemical mechanism at the base of the porous PANI film. The acid centers of PANI (protonated imine group) played an important role not only in two internal redox transform processes, but also in an external charge transfer reaction during the electrocatalytic reduction of oxygen. The incorporation of anionic AQS groups into PANI matrix to prepare electroactive PANI using the electrochemical doping-dedoping-redoping method is conceptually new, and may be extended to the development of new functional materials from many other conducting polymers and quinonoid compounds for wide applications in catalysis, sensors, molecular electronics, and so on.

Multi-holed clay nanotubes and their modification with a polyaniline nanolayer

A facile in situ mechanical–chemical polymerization method for synthesis of polyaniline/halloysite nanocomposites was developed. Electron micrographs of the composites showed novel multi-holed clay nanotubes modified with a porous polyaniline nanolayer. After removing clay tube cores, polyaniline nanotubes can be obtained. Moreover, novel multi-holed clay nanotubes were obtained after removing polymer shells.

Porous polyaniline exhibits highly enhanced electrochemical capacitance performance

Porous polyaniline (PANI) is prepared by using sodium dodecylsulfate as a soft template and ammonium persulfate as an oxidant. Transmission electron microscopy and nitrogen adsorption–desorption isotherms suggest the existence of both macro/mesopores and micropores, and the specific surface area of 211 m 2 g −1. As a result of its porous structure, the porous PANI exhibits highly enhanced utilization ratio during the charge–discharge cycles. This porous PANI also displays high cycle stability and rate capability.