A novel layered manganese oxide/poly(aniline-co-o-anisidine) nanocomposite and its application for electrochemical supercapacitor

A novel layered manganese oxide/poly(aniline-co-o-anisidine) nanocomposite [MnO₂/P(An-co-oAs)] was successfully synthesized by a delamination/reassembling process using P(An-co-oAs) ionomer and layered manganese oxide in aqueous solution. This nanocomposite obtained was then characterized by Fourier transform infrared (FTIR) spectra, X-ray diffraction (XRD), electron microscopy (SEM), and thermogravimetric (TG) analysis. X-ray diffraction and electron microscope analysis showed that the MnO₂/P(An-co-oAs) nanocomposite had a lamellar structure with increasing interlayer spacing. The MnO₂/P(An-co-oAs) nanocomposite exhibited substantially improved conductivity, which was near 100 times greater than that of its pristine MnO₂ (3.5 × 10⁻⁷ S cm⁻¹). The specific capacitance of the MnO₂/P(An-co-oAs) nanocomposite reached 262 F g⁻¹ in 1 M Na₂SO₄ at a current density of 1 A g⁻¹, which was significantly higher than that of either of its two pristine materials [MnO₂ (182 F g⁻¹) or P(An-co-oAs) (127 F g⁻¹)] owing to the synergic effect between the two pristine components. The fabrication mechanism of the nanocomposite was also proposed and discussed in this paper.     

A novel method to prepare nanostructured manganese dioxide and its electrochemical properties as a supercapacitor electrode

Nanostructured MnO₂ was synthesized by co-precipitation in the presence of Pluronic P123 surfactant and characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscope (SEM) and transmission electron microscope (TEM). The sample without surfactant was spherical with particle size on the submicron scale, whereas P123-assisted samples were all loose clew shapes, consisting of MnO₂ nanowires, 8-20 nm in diameter and 200-400 nm in length. The electrochemical performances of the as-prepared MnO₂ as the electrode materials for supercapacitors were evaluated by cyclic voltammetry and galvanostatic charge-discharge measurements in a solution of 1 M Na₂SO₄. The sample without surfactant exhibited a relatively low specific capacitance of 77 F g⁻¹, whereas the nanostructured MnO₂ prepared with 0.02% (wt%) P123 exhibited excellent pseudocapacitive behavior, with a maximum specific capacitance of 176 F g⁻¹.     

Development of new nanocomposite based on nanosized-manganese oxide and carbon nanotubes for high performance electrochemical capacitors

We report the synthesis of a new composite electrode based on nanosized-manganese oxide and carbon nanotubes (CNTs) by electrophoretic deposition of CNTs on a stainless steel (SS) substrate followed by direct spontaneous reduction of MnO₄⁻ ions to MnO₂ to form the multi-scaled SS-CNT-MnO₂ electrode. The resulting material was characterized by scanning electron microscopy, energy dispersive X-ray analysis, cyclic voltammetry and galvanostatic charge-discharge in a 0.65 M K₂SO₄ aqueous solution. The binderless SS-CNT-MnO₂ nanocomposite electrode shows a very high specific capacitance of 869 F/g of CNT-MnO₂ and good stability during long galvanostatic charge-discharge cycling. To the best of our knowledge, this is one of the highest capacitance for manganese oxide electrode ever reported. In addition to its applicability in electrochemical capacitors, this methodology could be extended to develop other high performance nanocomposite material electrodes based on carbon nanotubes and metal oxide for the future generation of electrochemical power sources.     

Supercapacitive properties of a nanowire-structured MnO2 electrode in the gel electrolyte containing silica

Nanowire-structured MnO₂ active materials were prepared by a chemical precipitation method and their supercapacitive properties for use in the electrodes of supercapacitors were investigated by means of cyclic voltammetry in an aqueous gel electrolytes consisting of 1 M Na₂SO₄ and fumed silica (SiO₂). The MnO₂ electrode showed a maximum specific capacitance of 151 F g⁻¹ after 1000 cycles at 100 mV s⁻¹ when using the gel electrolyte containing 3 wt.% of SiO₂, which is higher than 121 F g⁻¹ obtained when using the 1 M Na₂SO₄ liquid electrolyte alone.     

Textural and capacitive characteristics of MnO2 nanocrystals derived from a novel solid-reaction route

Nanostructured manganese dioxide (MnO₂) materials were synthesized via a novel room-temperature solid-reaction route starting with Mn(OAc)₂·4H₂O and (NH₄)₂C₂O₄·H₂O raw materials. In brief, the various MnO₂ materials were obtained by air-calcination (oxidation decomposition) of the MnC₂O₄ precursor at different temperatures followed by acid-treatment in 2 M H₂SO₄ solution. The influence of calcination temperature on the structural characteristics and capacitive properties in 1 M LiOH electrolyte of the MnO₂ materials were investigated by X-ray diffraction (XRD), infrared spectrum (IR), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) surface area analysis, cyclic voltammetry, ac impedance and galvanostatic charge/discharge electrochemical methods. Experimental results showed that calcination temperature has a significant influence on the textural and capacitive characteristics of the products. The MnO₂ material obtained at the calcination temperature of 300 °C followed by acid-treatment belongs to nano-scale column-like (or needle-like) γ,α-type MnO₂ mischcrystals. While, the MnO₂ materials obtained at the calcination temperatures of 400, 500, and 600 °C followed by acid-treatment, respectively, belong to γ-type MnO₂ with the morphology of aggregates of crystallites. The γ,α-MnO₂ derived from calcination temperature of 300 °C exhibited a initial specific capacitance lower than that of the γ-MnO₂ derived from the elevated temperatures, but presented a better high-rate charge/discharge cyclability.     

Electrosynthesis of poly(aniline-co-p-aminophenol) having electrochemical properties in a wide pH range

Copolymerization of aniline and p-aminophenol in aqueous sulfuric acid solutions was electrochemically performed using cyclic voltammetry on platinum electrodes. The monomer concentration ratio can strongly affect the copolymerization rate and electrochemical property of the copolymer. The optimum conditions for the copolymerization are that the potential sweep covers the −0.20 to 0.95 V (vs. SCE) potential range, and that a solution contains 0.18 M aniline, 0.02 M p-aminophenol and 0.50 M H₂SO₄. A resulting copolymer synthesized under the optimum conditions has a good electrochemical activity in 0.50 M solutions of Na₂SO₄ with pH ≤ 10.0. IR and XPS spectra indicate that -OH groups and SO₄²⁻ ions are contained in the resulting copolymer. The SEM images reveal that the microstructure of the copolymer depends on the monomer concentration ratio during the electrolysis.     

Factors influencing MnO2/multi-walled carbon nanotubes composite's electrochemical performance as supercapacitor electrode

Poor crystallined α-MnO₂ grown on multi-walled carbon nanotubes (MWCNTs) by reducing KMnO₄ in ethanol are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and Brunauer-Emmett-Telle (BET) surface area measurement, which indicate that MWCNTs are wrapped up by poor crystalline MnO₂ and BET areas of the composites maintain the same level of 200 m² g⁻¹ as the content of MWCNTs in the range of 0-30%. The electrochemical performances of the MnO₂/MWCNTs composites as electrode materials for supercapacitor are evaluated by cyclic voltammetry (CV) and galvanostatic charge-discharge measurement in 1 M Na₂SO₄ solution. At a scan rate of 5 mV s⁻¹, rectangular shapes could only be observed for the composites with higher MWCNTs contents. The effect of additional conductive agent KS6 on the electrochemical behavior of the composites is also studied. With a fixed carbon content of 25% (MWCNTs included), MnO₂ with 20% MWCNTs and 5% KS6 has the highest specific capacitance, excellent cyclability and best rate capability, which gives the specific capacitance of 179 F g⁻¹ at a scan rate of 5 mV s⁻¹, and remains 114.6 F g⁻¹ at 100 mV s⁻¹.     

Hydrated Mn(IV) oxide-exfoliated graphite composites for electrochemical capacitor

Commercially available low cost exfoliated graphite (EG, nominal diameter 130 μm) was used as a conductive substrate for electrochemical capacitor of hydrated Mn(IV) oxide, MnO₂·nH₂O. The MnO₂·nH₂O-EG composites were prepared by addition of EG to potassium permanganate solution, followed by 1 h stirring and then slow addition of manganese(II) acetate solution. By this procedure submicrometer or smaller sized MnO₂·nH₂O particles having mesopores of 6-12 nm in diameter were formed on the graphite sheets of EG. Although EG alone showed only about 2 F g⁻¹, the composites showed good rectangular cyclic voltammograms at 2-20 mV s⁻¹ in 1 mol L⁻¹ Na₂SO₄. The capacitance per net amount of MnO₂ increased proportionally with EG content, that is, utilization ratio of MnO₂ increased with EG content. The composites of MnO₂·nH₂O and smaller diameter of EG (nominal diameter 45 μm) or artificial graphite powder (average diameter 3.7 μm) showed fairly good performance at 2 mV s⁻¹, but with increasing potential scan rate the rectangular shape was distorted and capacitance decreased drastically. The results implies that sheet-like structure is more effective than small particles as conductive materials, when the formation procedure of composite is the same. Large sized EG may be a promising conductive material for electrochemical capacitors.     

Nanosized α-LiFeO2 as electrochemical supercapacitor electrode in neutral sulfate electrolytes

In this work we have explored the electrochemical properties of two lithiated iron oxide powders for supercapacitor purposes. These samples mainly consisted of α-LiFeO₂ in nanosized or micrometric form. Electrolyte was an aqueous 0.5 M Li₂SO₄ solution and voltage range studied was between 0 and −0.7 V vs. a Ag/AgCl reference electrode. As expected, electrochemical performance was dependent on the particle size. When electrolyte was deaerated a stable capacitance of ≈50 F g⁻¹ is provided by the nanosized sample for several hundred cycles. Other sulfate based salts (Na₂SO₄, K₂SO₄, Cs₂SO₄) were investigated as electrolytes but only Li₂SO₄ leads to a stable capacitance upon cycling, probably due to lithium intercalation. An hybrid cell consisting of this sample and MnO₂ as negative and positive electrodes, respectively, delivered 0.3 F cm⁻² (10 F g⁻¹). Although these values are lower than reported for other aqueous hybrid cell, α-LiFeO₂/MnO₂ asymmetric capacitor is interesting from both, an economic and an environmental point of view.     

Nanocomposites of manganese oxides and carbon nanotubes for aqueous supercapacitor stacks

Symmetrical supercapacitors and their serially connected two-cell stacks via a bipolar electrode were constructed with nanocomposites of manganese oxides and carbon nanotubes (MnO_x/CNTs) as the electrode materials. Nanocomposites with different contents of MnO_x were synthesised through the redox reaction between KMnO₄ and CNTs in aqueous solutions. The nanocomposites were characterised by scanning and transmission electron microscopy, BET nitrogen adsorption and X-ray diffraction before being examined in a three-electrode cell with a novel trenched graphite disc electrode by electrochemical means, including cyclic voltammetry, galvanostatic charging-discharging, and electrochemical impedance spectroscopy. The nanocomposites demonstrated capacitive behaviour in the potential range of 0-0.85 V (vs Ag/AgCl) in aqueous KCl electrolytes with less than 9% capacitance decrease after 9000 charging-discharging cycles. Symmetrical supercapacitors of identical positive and negative MnO_x/CNTs electrodes showed capacitive performance in good agreement with the individual electrodes (e.g. 0.90 V, 0.53 F, 1.3 cm²). The bipolarly connected two-cell stacks of the symmetrical cells exhibited characteristics in accordance with expectation, including a doubled stack voltage and reduced internal resistance per cell.     

Performance evaluation of CNT/polypyrrole/MnO2 composite electrodes for electrochemical capacitors

A ternary composite of CNT/polypyrrole/hydrous MnO₂ is prepared by in situ chemical method and its electrochemical performance is evaluated by using cyclic voltammetry (CV), impedance measurement and constant-current charge/discharge cycling techniques. For comparative purpose, binary composites such as CNT/hydrous MnO₂ and polypyrrole/hydrous MnO₂ are prepared and also investigated for their physical and electrochemical performances. The specific capacitance (SC) values of the ternary composite, CNT/hydrous MnO₂ and polypyrrole/hydrous MnO₂ binary composites estimated by CV technique in 1.0 M Na₂SO₄ electrolyte are 281, 150 and 35 F g⁻¹ at 20 mV s⁻¹ and 209, 75 and 7 F g⁻¹ at 200 mV s⁻¹, respectively. The electrochemical stability of ternary composite electrode is investigated by switching the electrode back and forth for 10,000 times between 0.1 and 0.9 V versus Ag/AgCl at 100 mV s⁻¹. The electrode exhibits good cycling stability, retaining up to 88% of its initial charge at 10,000th cycle. A full cell assembled with the ternary composite electrodes shows a SC value of 149 F g⁻¹ at a current loading of 1.0 mA cm⁻² during initial cycling, which decreased drastically to a value of 35 F g⁻¹ at 2000th cycle. Analytical techniques such as scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), Brunauer-Emmet-Teller (BET) surface area measurement and inductively coupled plasma-atomic emission spectrometry (ICP-AES) are also used to characterize the composite materials.     

Enhanced electrochemical stability and charge storage of MnO2/carbon nanotubes composite modified by polyaniline coating layer in acidic electrolytes

Manganese dioxide/multiwalled carbon nanotubes (MnO₂/MWCNTs) were synthesized by chemically depositing MnO₂ onto the surface of MWCNTs wrapped with poly(sodium-p-styrenesulfonate). Then, polyaniline (PANI) with good supercapacitive performance was further coated onto the MnO₂/MWCNTs composite to form PANI/MnO₂/MWCNTs organic-inorganic hybrid nanoarchitecture. Electrochemical performance of the hybrid in Na₂SO₄-H₂SO₄ mixed acidic electrolytes was evaluated by cyclic voltammetry (CV) and chronopotentiometry (CP) in detail. Comparative electrochemical tests revealed that the hybrid nanoarchitecture could operate in the acidic medium due to the protective modification of PANI coating layer onto the MnO₂/MWCNTs composite, and that its electrochemical behavior was greatly dependent upon the concentration of protons in the acidic electrolytes. Here, PANI not only served as a physical barrier to restrain the underlying MnO₂/MWCNTs composite from reductive-dissolution process so as to make the novel ternary hybrid material work in acidic medium to enhance the utilization of manganese oxide as much as possible, but also was another electroactive material for energy storage in the acidic mixed electrolytes. It was due to the existence of PNAI layer that an even larger specific capacitance (SC) of 384 F g⁻¹ and a much better SC retention of 79.9% over 1000 continuous charge/discharge cycles than those for the MnO₂/MWCNTs nanocomposite were delivered for the hybrid in the optimum 0.5 M Na₂SO₄-0.5 M H₂SO₄ mixed acidic electrolyte.     

Voltammetric characterization of an iridium oxide-based system: the pseudocapacitive nature of the Ir0.3Mn0.7O2 electrode

Mixtures of IrO₂+MnO₂ (30:70 mol%) have been electrochemically studied by cyclic voltammetry (CV) in acid solution. The crystalline structure, morphology and the electrochemical properties of the electrodes have been studied as a function of the annealing temperature. X-ray diffraction analysis (XRD), show absence of Mn₂O₃ phase formation and suggest the possible of formation of a solid solution of IrO₂ and MnO₂ mainly between 400 and 450 °C. The voltammetric behavior depends on the potential cycle number and annealing temperature employed in the preparation of the oxide layer. A good potential window in aqueous H₂SO₄ and high electroactive area are obtained due to the contribution of Ir redox transitions. Energy-dispersive X-ray (EDX) and scanning electron microscopy (SEM) analysis suggest an enrichment of the Ir content on the surface at the cost of the dissolution of the manganese present in the film when the electrode is submitted to the continuous potential scan. The electrodes have been found to perform well in electrochemical capacitor applications with a specific capacitance close to 550 F g⁻¹. The large capacitance exhibited by this system arises from a combination of the double-layer capacitance and pseudocapacitance associated with surface redox-type reactions.     

Characterization and performance of hydrous manganese oxide prepared by electrochemical method and its application for supercapacitors

Hydrous manganese oxide was deposited on graphite substrates at anodic potentials of 0.5-0.95 V versus saturated calomel electrode (SCE) in 0.25 M Mn(CH₃COO)₂ solution at 25 °C. Morphology of manganese oxide prepared was examined by scanning electron microscopy (SEM). Manganese oxide deposited at various anodic potentials was evaluated by cyclic voltammetry with various potential scan rates in different electrolytes. Results indicated that the pseudocapacitive behaviors of manganese oxide were excellent both in 2 M KCl and 2 M (NH₄)₂SO₄ solutions at room temperature. Manganese oxide deposited at 0.5 V versus SCE showed better capacitive behaviors, the specific capacitances were 275 F/g in 2 M KCl solution and 310 F/g in 2 M (NH₄)₂SO₄ solution, respectively. Besides, better electrochemical reversibility could be obtained in 2 M KCl solution.     

Factors influencing the structure of electrochemically prepared α-MnO2 and γ-MnO2 phases

The α- and γ-phases of MnO₂ prepared by electrolysis of MnSO₄ and M_xSO₄ (where M = Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺ or Mg²⁺) in aqueous solutions at various pH and voltage E_v values under ambient conditions have been systematically studied. The structures of powdery MnO₂ produced are found to depend on the radius of the M^z+ counter cation in addition to the pH and E_v conditions. In order to achieve the α-phase for MnO₂ formation under neutral pH condition, the radius of counter cation must be equal to or greater than 1.41 Å, the size of the K⁺ cation. The relative concentration ratio of [MnO₄⁻]_transient/[Mn²⁺], which is related to the pH-E_v conditions, also affects the structure of MnO₂ produced with counter ions smaller than K⁺. For samples prepared in acidified solution with the counter ions of Li⁺, Na⁺ or Mg²⁺ at 2.2 V, the electrolysis products display the γ-MnO₂ phase while those prepared at 2.8 V electrolysis produce a mixture of γ-MnO₂ and α-MnO₂ phases. Single phase of α-MnO₂ is identified in the 5 V electrolysis products. Furthermore, the valence state of manganese was found to decrease as the applied voltage was reduced from 5.0 to 2.2 V. This implies that the lower [MnO₄⁻]_transient/[Mn²⁺] ratio or the less oxidative condition is responsible for the non-stoichiometric MnO₂ structure with oxygen deficiency.     

Preparation and characterization of manganese oxide/CNT composites as supercapacitive materials

Manganese oxide was synthesized and dispersed on carbon nanotube (CNT) matrix by thermally decomposing manganese nitrates. CNTs used in this paper were grown directly on graphite disk by chemical vapor deposition technique. The capacitive behavior of manganese oxide/CNT composites was investigated by cyclic voltammetry and galvanostatic charge–discharge method in 1 M Na₂SO₄ aqueous solutions. When the loading mass of MnO₂ is 36.9 μg cm^− 2, the specific capacitance of manganese oxide/CNT composite (based on MnO₂) at the charge–discharge current density of 1 mA cm^− 2 equals 568 F g^− 1. Additionally, excellent charge–discharge cycle stability (ca. 88% value of specific capacitance remained after 2500 charge–discharge cycles) and power characteristics of the manganese oxide/CNT composite electrode can be observed. The effect of loading mass of MnO₂ on specific capacitance of the electrode has also been investigated.     

Electrochemical behavior of LiCoO2 in a saturated aqueous Li2SO4 solution

The electrochemical behavior of a commercial LiCoO₂ with spherical shape in a saturated Li₂SO₄ aqueous solution was investigated with cyclic voltammetry and electrochemical impedance spectroscopy. Three redox couples at E_SCE = 0.87/0.71, 0.95/0.90 and 1.06/1.01 V corresponding to those found at ELi/Li⁺=4.08/3.83, 4.13/4.03 and 4.21/4.14 V in organic electrolyte solutions were observed. The diffusion coefficient of lithium ions is 1.649 × 10⁻¹⁰ cm² s⁻¹, close to the value in organic electrolyte solutions. The results indicate that the intercalation and deintercalation behavior of lithium ions in the Li₂SO₄ solution is similar to that in the organic electrolyte solutions. However, due to the higher ionic conductivity of the aqueous solution, current response and reversibility of redox behavior in the aqueous solution are better than in the organic electrolyte solutions, suggesting that the aqueous solution is favorable for high rate capability. The charge transfer resistance, the exchange current and the capacitance of the double layer vary with the charge voltage during the deintercalation process. At the peak of the oxidation (0.87 V), the charge transfer resistance is the lowest. These fundamental results provide a good base for exploring new safe power sources for large scale energy storage.     

High dispersion of γ-MnO2 on well-aligned carbon nanotube arrays and its application in supercapacitors

The well-aligned carbon nanotube arrays (ACNTs) were used as supporting material and the γ-MnO₂/ACNT electrode with high dispersion of γ-MnO₂ has been prepared by electrochemically induced deposition method. The crystal structure and morphology of the γ-MnO₂/ACNT electrode were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The capacitive properties of γ-MnO₂/ACNT electrode were characterized by cyclic voltammetry and galvanostatic charge–discharge method. The specific capacitance of the γ-MnO₂/ACNT electrode is as high as 784 F g^− 1 based on γ-MnO₂ and 234 F g^− 1 based on γ-MnO₂/ACNT composites in 0.1 M Na₂SO₄ aqueous solution from 0 to 1 V when the charge–discharge current density is 1 mA cm^− 2. Additionally, the electrode shows excellent power characteristics, high electrochemical reversibility and excellent long-term charge–discharge cycle stability.     

Polypyrrole and La1−xSrxMnO3 (0≤ x ≤0.4) composite electrodes for electroreduction of oxygen in alkaline medium

Composite G/PPy/PPy(La_1−xSr_xMnO₃)/PPy electrodes made of the perovskite La_1−xSr_xMnO₃ embedded into a polypyrrole (PPy) layer, sandwiched between two pure PPy films, electrodeposited on a graphite support were investigated for electrocatalysis of the oxygen reduction reaction (ORR). PPy and PPy(La_1−xSr_xMnO₃) (0≤ x ≤0.4) successive layers have been obtained on polished and pretreated graphite electrodes following sequential electrodeposition technique. The electrolytes used in the electrodeposition process were Ar saturated 0.1 mol dm⁻³ pyrrole (Py) plus 0.05 mol dm⁻³ K₂SO₄ with and without containing a suspension of 8.33 g L⁻¹ oxide powder. Films were characterized by XRD, SEM, linear sweep voltammetry, cyclic voltammetry (CV) and electrochemical impedance (EI) spectroscopy. Electrochemical investigations were carried out at pH 12 in a 0.5 mol dm⁻³ K₂SO₄ plus 5 mmol dm⁻³ KOH, under both oxygenated and deoxygenated conditions. Results indicate that the porosity of the PPy matrix is considerably enhanced in presence of oxide particles. Sr substitution is found to have little influence on the electrocatalytic activity of the composite electrode towards the ORR. However, the rate of oxygen reduction decreases with decreasing pH of the electrolyte from pH 12 to pH 6. It is noteworthy that in contrast to a non-composite electrode of the same oxide in film form, the composite electrode exhibits much better electrocatalytic activity for the ORR.     

Capacitive performance of polyaniline/manganese dioxide nanofiber microsphere

This work has obtained polyaniline/manganese dioxide (PANI/MnO₂) nanofibers microsphere by interfacial chemical synthesis with 4‐amino‐thiophenol (4‐ATP) as the structure‐directing agent on the Au substrate. The cyclic voltammograms, galvanostatic charge–discharge, and electrochemical impedance spectroscopy were used to determine their capacitive performance. Powder X‐ray diffraction, thermogravimetry and differential scanning calorimetry, Fourier transformed infrared spectroscopy, Brunauer–Emmett–Teller surface area measurements, and scanning electron microscope were performed for physical and chemical characterization. The effect of 4‐ATP and acids on the capacitive performance of PANI/MnO₂ nanofibers microsphere was elucidated. The as‐prepared PANI/MnO₂ was nanofiber about 30 nm diameters, and they further self‐assembled into sphere. Its specific capacitance is up to 765 F g^?1 at 1.0 mA cm^?2 in 1.0M Na₂SO₄ solution. And it shows a high stability with a capacitance fade of only 14.9% after 400 charge–discharge cycles. The symmetric capacitor of PANI/MnO₂ (PM10+)/PANI/MnO₂ (PM10?) is assembled in 1.0M Na₂SO₄ solution, and its capacitive performance is compared with that of PANI (+)/PANI (?) and MnO₂ (+)/MnO₂ (?). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40575.