The effect of anions on the electrochemical properties of polyaniline for supercapacitors

Modulation of polyaniline memristive device switching voltage by nucleotide-free analogue of vitamin B12

Memristive devices offer essential properties to become a part of the next-generation computing systems based on neuromorphic principles. Organic memristive devices exhibit a unique set of properties which makes them an indispensable choice for specific applications, such as interfacing with biological systems. While the switching rate of organic devices can be easily adjusted over a wide range through various methods, controlling the switching potential is often more challenging, as this parameter is intricately tied to the materials used. Given the limited options in the selection conductive polymers and the complexity of polymer chemical engineering, the most straightforward and accessible approach to modulate switching potentials is by introducing specific molecules into the electrolyte solution. In our study, we show polyaniline (PANI)-based device switching potential control by adding nucleotide-free analogue of vitamin B12, aquacyanocobinamide, to the electrolyte solution. The employed concentrations of this molecule, ranging from 0.2 to 2 mM, enabled organic memristive devices to achieve switching potential decrease for up to 100 mV, thus providing a way to control device properties. This effect is attributed to strong aromatic interactions between PANI phenyl groups and corrin macrocycle of the aquacyanocobinamide molecule, which was supported by ultraviolet-visible spectra analysis.

Effects of Mechanical Deformation on the Opto-Electronic Responses, Reactivity, and Performance of Conjugated Polymers: A DFT Study

The development of polymers for optoelectronic applications is an important research area; however, a deeper understanding of the effects induced by mechanical deformations on their intrinsic properties is needed to expand their applicability and improve their durability. Despite the number of recent studies on the mechanochemistry of organic materials, the basic knowledge and applicability of such concepts in these materials are far from those for their inorganic counterparts. To bring light to this, here we employ molecular modeling techniques to evaluate the effects of mechanical deformations on the structural, optoelectronic, and reactivity properties of traditional semiconducting polymers, such as polyaniline (PANI), polythiophene (PT), poly (p-phenylene vinylene) (PPV), and polypyrrole (PPy). For this purpose, density functional theory (DFT)-based calculations were conducted for the distinct systems at varied stretching levels in order to identify the influence of structural deformations on the electronic structure of the systems. In general, it is noticed that the elongation process leads to an increase in electronic gaps, hypsochromic effects in the optical absorption spectrum, and small changes in local reactivities. Such changes can influence the performance of polymer-based devices, allowing us to establish significant structure deformation response relationships.

Iridium and Ruthenium Modified Polyaniline Polymer Leads to Nanostructured Electrocatalysts with High Performance Regarding Water Splitting

The breakthrough in water electrolysis technology for the sustainable production of H₂, considered as a future fuel, is currently hampered by the development of tough electrocatalytic materials. We report a new strategy of fabricating conducting polymer-derived nanostructured materials to accelerate the electrocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and water splitting. Extended physical (XRD, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX)) and electrochemical (cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS)) methods were merged to precisely characterize the as-synthesized iridium and ruthenium modified polyaniline (PANI) materials and interrogate their efficiency. The presence of Ir(+III) cations during polymerization leads to the formation of Ir metal nanoparticles, while Ru(+III) induces the formation of RuO₂ oxide nanoparticles by thermal treatment; they are therefore methods for the on-demand production of oxide or metal nanostructured electrocatalysts. The findings from using 0.5 M H₂SO₄ highlight an ultrafast electrochemical kinetic of the material PANI-Ir for HER (36 - 0 = 36 mV overpotential to reach 10 mA cm^-2 at 21 mV dec^-1), and of PANI-Ru for OER (1.47 - 1.23 = 240 mV overpotential to reach 10 mA cm^-2 at 47 mV dec^-1), resulting in an efficient water splitting exactly at its thermoneutral cell voltage of 1.45 V, and satisfactory durability (96 h).

Improving the Performance of a Graphite Foil/Polyaniline Electrode Material by a Thin PEDOT:PSS Layer for Application in Flexible, High Power Supercapacitors

In this study, we present a novel strategy for enhancing polyaniline stability and thus obtaining an electrode material with practical application in supercapacitors. A promising (graphite foil/polyaniline/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) GF/PANI/PEDOT:PSS) electrode material was characterized and used in the construction of a symmetric supercapacitor that provides an outstanding high power density. For this purpose, the electropolymerization of PANI was carried out on a graphite foil and then a thin protective layer of PEDOT:PSS was deposited. The presence of the nanometer PEDOT:PSS layer made it possible to widen the electroactivity potential range of the electrode material. Moreover, the synergy between materials positively affected the amount of accumulated charge, and thus the thin PEDOT:PSS layer contributed to enhancing the specific capacity of the electrode material. The electrochemical performance of the GF/PANI/PEDOT:PSS electrode, as well as the symmetrical supercapacitor, was investigated by cyclic voltammetry and galvanostatic charge/discharge cycles in 1 M H2SO4 at room temperature. The fabricated electrode material shows a high specific capacitance (Csp) of 557.4 Fg-1 and areal capacitance (Careal) of 2600 mF·cm-2 in 1 M H2SO4 at a current density of 200 mA·cm-2 (~4 A·g-1). The supercapacitor performance was studied and the results show that a thin PEDOT:PSS layer enables cycling stability improvement of the device from 54% to 67% after 10,000 cycles, and provides a high specific capacity (159.8 F·g-1) and a maximum specific power (18,043 W·kg-1) for practical applications.

One-pot mechanochemical exfoliation of graphite and in situ polymerization of aniline for the production of graphene/polyaniline composites for high-performance supercapacitors

Graphene/polyaniline composites have attracted considerable attention as high-performance supercapacitor electrode materials; however, there are still numerous challenges for their practical applications, such as the complex preparation process, high cost, and disequilibrium between energy density and power density. Herein, we report an efficient method to produce graphene/polyaniline composites via a one-pot ball-milling process, in which aniline molecules act as both the intercalator for the exfoliation of graphite and the monomer for mechanochemical polymerization into polyaniline clusters on the in situ exfoliated graphene sheets. The graphene/polyaniline composite electrode delivered a large specific capacitance of 886 F g⁻¹ at 5 mV s⁻¹ with a high retention of 73.4% at 100 mV s⁻¹. The high capacitance and rate capability of the graphene/polyaniline composite can contribute to the fast electron/ion transfer and dominantly capacitive contribution because of the synergistic effects between the conductive graphene and pseudocapacitive polyaniline. In addition, a high energy density of 40.9 W h kg⁻¹ was achieved by the graphene/polyaniline-based symmetric supercapacitor at a power density of 0.25 kW kg⁻¹, and the supercapacitor also maintained 89.1% of the initial capacitance over 10 000 cycles.

Efficient ball-milling production of graphene/polyaniline composites as supercapacitor electrodes with enhanced capacitive contribution, rate capability, and specific capacitance.

Hydrothermal synthesis of PANI nanowires for high-performance supercapacitor

Polyaniline nanowires (PANI NWs) were synthesized under different temperatures through a facile hydrothermal method and used as electrodes for high-performance pseudocapacitor. The resulting samples were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron micrographs, thermogravimetric analysis, and X-ray photoelectron spectroscopy. Electrochemical properties of these PANI electrodes are studied by cyclic voltammetry, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy in 0.5M H2SO4 aqueous solution. The highest specific capacitance is obtained on the PANI NWs synthesized under 80°C (PANI-80) with 540.0 F g−1 at current density of 0.5 A g−1 accompanied with 82% specific capacitance retention after 1000 charge discharge cycles at 5 A g−1 current density.

Recent Progress on Graphene/Polyaniline Composites for High-performance Supercapacitors

Electrode materials are crucial for the electrochemical performance of supercapacitors. In view of the high specific surface area, high conductivity of graphene nanosheets and the high pseudocapacitance of polyaniline (PANI), the combination of graphene with PANI has become a research hotspot. In this work, we summarize the recent advance on the synthesis of PANI and graphene/PANI composites, and their application in supercapacitors. The synthesis of PANI is the basis of preparing graphene/PANI composites, so we first introduce the synthesis methods of PANI. Then, the advances of two dimensional (2D) and three dimensional (3D) graphene/PANI composites are summarized according to the inherent feature of graphene. The 2D composites of pristine graphene and functionalized graphene with PANI are introduced separately; furthermore, the 3D composites are classified into three sections, including flexible graphene/PANI composites, graphene framework based composites, and printable graphene/PANI composites. At last, aiming at solving the current challenges of graphene/PANI composites, we put forward some strategies for preparing high performance graphene/PANI composite electrodes.