Sunghun Cho

Enhanced Electrochemical Performance of Highly Porous Supercapacitor Electrodes Based on Solution Processed Polyaniline Thin Films

Enhancement to the electrochemical performance of supercapacitor electrodes were realized by incorporating highly porous conductive polymer films prepared with solution-processed polyaniline. The resultant nanostructures contained characteristic pores measuring 30-150 nm. Such electrodes generated from a solution of polyaniline-camphorsulfonic acid (PANI/CSA) exhibited higher porosity and electro-catalytic activity than those generated from conventional PANI nanomaterials. These improvements were attributed to faster ion diffusion at the PANI electrode/electrolyte interface. The highest specific capacitance observed for a supercapacitor fabricated with a porous PANI electrode obtained was 361 F g(-1) at 0.25 A g(-1), which is more than twice that of an equivalent electrode made with pristine PANI. Furthermore, supercapacitors made with highly porous PANI electrodes exhibited high electrochemical stability and rate performances.

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.

Screen-Printable and Flexible RuO2 Nanoparticle-Decorated PEDOT:PSS/Graphene Nanocomposite with Enhanced Electrical and Electrochemical Performances for High-Capacity Supercapacitor.

UNLABELLED This work describes a ternary screen-printed electrode system, composed of aqueous poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonic acid) ( PEDOT PSS), graphene, and hydrous ruthenium(IV) oxide (RuO2) nanoparticles for use in high-performance electrochemical capacitors. As a polymeric binder, PSS allows stable dispersion of graphene and hydrous RuO2 nanoparticles (NPs) in an aqueous PEDOT PSS system through electrostatic stabilization, ensuring better utilization of the three components. Additional PSS molecules were added to optimize the solution viscosity to obtain screen-printed electrodes. The effects of graphene and hydrous RuO2 NPs on the electrical and electrochemical properties of PEDOT PSS were systematically investigated. The graphene sheets greatly enhanced the charge-transport properties, such as the doping level and conjugation length, through strong π-π stacking interactions with the PEDOT structure. The hydrous RuO2 NPs anchored to the PEDOT PSS/graphene surfaces facilitated redox reactions with the surrounding electrolyte, and significantly enhanced the specific capacitance of the electrode materials. The resulting RuO2/PEDOT:PSS/graphene electrode with a thickness of ∼5 μm exhibited high conductivity (1570 S cm(-1)), a large specific capacitance (820 F g(-1)), and good cycling stability (81.5% after 1000 cycles).

Fabrication of a polyaniline/MoS2 nanocomposite using self-stabilized dispersion polymerization for supercapacitors with high energy density

In this report, a polyaniline/MoS2 nanocomposite has been firstly produced using a self-stabilized dispersion polymerization method. The synthesized polyaniline/MoS2 nanocomposite exhibited a remarkably high electrical conductivity of ca. 28.6 S cm−1, which is higher than other previously reported MoS2-based composites. Additionally, the PANI/MoS2 nanocomposite exhibited substantially improved capacitance (ca. 400 F g−1) compared to pristine MoS2 nanosheets (ca. 3 F g−1) and PANI (ca. 232 F g−1) and enhanced cycling stability (retention rate of 84%) in comparison with pure PANI (retention rate of 62%). Furthermore, the PANI/MoS2 nanocomposite demonstrated a higher energy density (4.7 W h kg−1 at 1000 W kg−1) than conventional electrochemical capacitors and other previously reported carbon and carbon/conducting polymer based electrochemical capacitors owing to its high utilizing of pseudocapacitance attributed to high electrical conductivity. What is more, the synthesized PANI/MoS2 nanocomposite demonstrated good rate capability and a good power characteristic as the supercapacitor electrode by keeping its high energy density (3.8 W h kg−1) at a high power density (2000 W kg−1) due to the existence of sufficient empty space between interconnected PANI nanofibers and high electrical conductivity of the PANI/MoS2 nanocomposite.

Shape-controlled polyaniline chemiresistors for high-performance DMMP sensors: effect of morphologies and charge-transport properties

Shape-designed polyaniline (PANI) nanomaterials (nanoparticles, nanorods, and nanofibers) are prepared by adjusting the amount of the oxidizing agent and the monomer during chemical oxidation polymerization. The charge-transport properties of the precisely controlled PANI geometries at the nanometer scale were systematically investigated to identify the optimal sensing conditions to detect the nerve gas agent dimethyl methylphosphonate (DMMP). Intrinsically, the aspect ratio of PANI nanomaterials can change with the oxidation state, which is closely related to the doping level and conjugation length. Our results suggest that the transport behavior of the nanomaterials is highly dependent on their aspect ratios. Extrinsically, PANI nanomaterials deposited onto gold-interdigitated microelectrodes are able to form stable conductive channels by minimizing the contact resistance between the microelectrodes and the nanomaterials. High-performance chemiresistive sensors based on PANI nanomaterials were successfully fabricated and their sensing properties were demonstrated. The real-time response of a DMMP-sensor based on PANI nanofibers was better than that of sensors based on PANI nanoparticles or nanorods. High-performance chemiresistive sensors with a low minimum detection level (MDL, 5 ppb) could be designed through comparative studies of charge-transport properties.

Graphene/polyaniline/poly(4-styrenesulfonate) hybrid film with uniform surface resistance and its flexible dipole tag antenna application.

A graphene/polyaniline/poly(4-styrenesulfonate) (G/PANI/PSS)-based conducting paste is successfully fabricated by introducing a PANI/PSS nanofiller into a multilayer graphene matrix by mechanical blending. As a compatibilizer, the PSS binder increases the dispersibility, interfacial interactions, and mechanical interlocking between the multilayer graphene matrix and PANI, thereby allowing surface resistance with narrow distribution. High concentrations of this PSS binder, obtained using ex situ polymerization, further improve the adhesion of the hybrid film to a flexible substrate. The minimum surface resistance of the screen-printed G/PANI/PSS hybrid film is approximately 10 Ω sq(-1) for a 70 μm uniform thickness. When bent to angles of -30°, the flexible hybrid film exhibits an approximately 6% decrease in surface resistance. The surface resistance after 500 bending cycles increases by only 10 Ω sq(-1) , which is 14 times that of smaller, graphene-based thin films. The micropatterned, screen-printed G/PANI/PSS hybrid film is evaluated as a practical dipole tag antenna. High-resolution patterns are formed in the hybrid film by the inherently high surface tension and the properties of grains within the domain-based structure. The G/PANI/PSS-based dipole tag antenna has a bandwidth of 28.7 MHz, a high transmitted power efficiency of 98.5%, and a recognition distance of 0.42 m at a mean frequency of 910 MHz. These characteristics indicate that the G/PANI/PSS-based dipole tag antenna could be used as a signal-receiving apparatus, much like a radio-frequency identification tag, for detecting nearby objects.

Highly porous nanostructured polyaniline/carbon nanodots as efficient counter electrodes for Pt-free dye-sensitized solar cells

We report a novel method for synthesizing highly porous polyaniline (PANI) using carbon nanodots (CNDs) as a nucleating agent and demonstrate their use as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). CNDs surrounded with aniline act as efficient nuclei in the polymerization reaction. CNDs disrupt undesirable secondary growth reactions leading to the formation of an agglomerated structure, and organize the highly porous PANI structures with a large surface area (43.6 m2 g−1). Moreover, the presence of CNDs in the polymerization mixture facilitates generation of head-to-tail dimers, and enhances the degree of para-coupling in the molecular structure of PANI. As a result of these nucleation effects, the fabricated PANI-CND films exhibit an increased electrical conductivity of ca. 774 S cm−1. When used as a CE in DSSCs, PANI-CND CEs exhibit a superior power conversion efficiency (η = 7.45%) to those of conventional platinum (η = 7.37%) and pristine PANI CEs (η = 5.60%).

High-sensitivity hydrogen gas sensors based on Pd-decorated nanoporous poly(aniline-co-aniline-2-sulfonic acid):poly(4-styrenesulfonic acid)

We report a novel method for fabricating Pd-decorated nanoporous poly(aniline-co-aniline-2-sulfonic acid):poly(4-styrenesulfonic acid) (P(ANI-co-ASA):PSS) nanostructures and demonstrate their use as sensing elements for hydrogen (H2) gas sensors. Both co-monomers and PSS provide sufficient –SO3H groups to effectively anchor palladium nanoparticles and lead to enhanced interactions with H2 gas, while retaining the charge transport properties of the P(ANI-co-ASA):PSS. The pores were 10–30 nm in diameter and were readily formed on the Pd-decorated P(ANI-co-ASA):PSS surfaces by introducing water-soluble porogen agents. The pores enlarged the surface area available for interaction with the H2 gas molecules, resulting in much higher sensitivity compared with both the non-porous Pd-decorated P(ANI-co-ASA):PSS and the pristine P(ANI-co-ASA):PSS. We achieved a detection limit of 5 ppm for H2 gas using a conducting polymer at room temperature.

Platinum-decorated carbon nanoparticle/polyaniline hybrid paste for flexible wideband dipole tag-antenna application

Recently, tremendous effort has been devoted to the production of materials for flexible device systems due to the advancement of portable electronic devices. Solution-processed conducting polymers (CPs), as a promising approach, have been extensively studied owing to facile synthesis, high electrical conductivity, and various morphologies with diverse substrates. Here we report the demonstration of platinum decorated carbon nanoparticle embedded polyaniline:camphorsulfonic acid (Pt_C/PANI:CSA) hybrid paste for flexible electronic devices. First, platinum decorated carbon nanoparticles (Pt_C) were fabricated by chemical reduction of platinum cations following the carbonization step. The as-prepared Pt_C were added to the aniline monomer solution and then polymerization of aniline occurred to form the hybrid PANI:CSA based paste (Pt_C/PANI:CSA). The Pt_C/PANI:CSA was printed as a micro-pattern and exhibited a high electrical conductivity (792 S cm−1) with flexible stability. Furthermore, it was applied to dipole tag-antenna application which displayed a wide bandwidth (0.55 GHz) and a high transmitted power efficiency (99.6%).