The ordered polyaniline nanowires wrapped on the polypyrrole nanotubes as electrode materials for electrochemical energy storage

Carbon Nanofibers as Supporting Substrate for Growth of Polyaniline Nanorods on Fe2O3 Nanoneedles toward Electrochemical Energy Storage

Iron-oxide (Fe2O3) nanoneedles were first in situ grown on the surface of carbon nanofibers (CNFs) using hydrothermal and N2 annealing process, and then polyaniline (PANI) was coated on the Fe2O3 nanoneedles to form network-like nanorods through dilute solution polymerization. The PANI/Fe2O3/CNFs binder-free electrode exhibited a high specific capacitance of 603 F/g at 1 A/g with good rate capability. (The capacitance loss was about 48.3% when the current density increased from 1.0 to 5.0 A/g.) It was caused by the fact that the PANI/Fe2O3/CNFs with a well-connected structure could provide a continuous electron transport path and improve the conductivity of the entire electrode. The solid-state hybrid PANI/Fe2O3/CNFs∥PANI/Fe2O3/CNFs symmetric device also achieved a high energy density of 29.85 Wh/kg at a power density of 500 W/kg. This universal compatible synthetic method for the PANI/Fe2O3/CNFs electrode could extend to other supercapacitor electrode systems, making it easy to fabricate various ternary electrodes for supercapacitors.

Agile soft template array fabrication of one-dimensional (1D) polyaniline nanocomposite fibers for hydrogen storage

Polyaniline-Zn/V2O5 nanocomposites were prepared in the presence of toluene-4-sulfonic acid monohydrate as an anionic surfactant via an in situ oxidation polymerization method. The structural study of the nanocomposites was carried out using FTIR and XRD analysis, and their surface morphology was characterized through SEM analysis. The BET surface area of a 3 wt% nanocomposite was 386 m2 g-1, which is higher compared to that of PANI. The Kelvin two probe method was used to study DC conductivity, and it was found that the conductivity increases with increasing temperature. Among all the PANI nanocomposites, 3 wt% PANI-Zn/V2O5 shows a high conductivity of 13.8 S cm-1. Cyclic voltammetry results show the characteristic oxidation-reduction peaks at 0.93 V and 0.24 V for polyaniline and its nanocomposites, respectively. Hydrogen absorption studies were carried out using volumetric sorption measurement technique. At room temperature, it was found that the hydrogen adsorption capacity of polyaniline fibres is about 4.5 wt%, and its absorption capacity increases two-fold upon increasing the temperature up to 60 °C. Conversely, the 3 wt% PANI-Zn/V2O5 nanocomposite showed a high absorption capacity of 6.6 wt% compared with other compositions, which is may be due to the presence of nitrogen (N) molecules in polyaniline and its particular porous fiber architecture.

High energy density flexible Zn-ion hybrid supercapacitors with conductive cotton fabric constructed by rGO/CNT/PPy nanocomposite

Fiber-shaped energy-storage devices for high energy and power density are crucial to power wearable electronics. In this work, reduced graphene oxide/carbon nanotubes/polypyrrole (GCP-op) cotton fabric with the optimal performance is prepared via a facile and cost-effective dipping-drying together with chemical polymerization approach. The structural characterizations confirm that the GCP-op cotton fabric has been successfully attached with numerous nanoparticles and carbon nanotubes, which can serve as a channel for electronical transfer. And GCP-op cotton fabric electrode displays admirable areal specific capacitance with 8397 mF cm-2at 1 mA cm-2. By combining GCP-op cathode with zinc anode, a GCP-op//PAM/ZnCl2//Zn flexible Zn-ion hybrid supercapacitor (FZHSC) is produced with 2 M polyacrylamide/ZnCl2(PAM/ZnCl2) hydrogel as the gel electrolyte. The FZHSC has superior cycle stability of 88.2%, outstanding energy density of up to 158μWh cm-2and power density at 0.5 mW cm-2. The remarkable performance proves that PPy-based material can provide more options for design and fabricate high energy flexible Zn-ion hybrid supercapacitors.

Selective separation of monovalent anions by PPy/pTS membrane electrodes in redox transistor electrodialysis

Selective separation of nitrate over chloride is crucial for eutrophication mitigation and nitrogen resource recovery but remains a challenge due to their similar ionic radius and the same valence. Herein, a polypyrrole membrane electrode (PME) was fabricated by polymerization of pyrrole (Py) and p-toluenesulfonate (pTS), which was used as a working electrode in redox transistor electrodialysis. The anions in the source solution were first incorporated into the PME at reduction potentials and then released to receiving solution at oxidation potentials. Pulse widths and potentials were optimized to maximize the ion separation performance of PME, resulting in the improvement of NO₃^-/Cl^- separation factor up to 6.93. The ion distributions in various depths of PME indicated that both NO₃^- and Cl^- were incorporated into PME at negative potentials. Then, NO₃^- was preferentially released from PME at positive potentials, but most Cl^- was retained. This was ascribed to the high binding energy between Cl^- and PPy/pTS structure, which was 51.4% higher than that between NO₃^- and PPy/pTS structure. Therefore, the higher transport rate of NO₃^- in comparison with Cl^- was achieved, leading to a high NO₃^- selectivity over Cl^-. This work provides a promising avenue for the selective separation of nitrate over chloride, which may contribute to nitrogen resource recycling and reuse.

In Situ Growth of MnO2 Nanosheets on a Graphite Flake as an Effective Binder-Free Electrode for High-Performance Supercapacitors

In this work, manganese dioxide (MnO2) nanosheets in situ loaded on a high-purity graphite flake (GF) were prepared by one-step hydrothermal deposition. It was found that the specific capacitance value of a single MnO2/GF electrode was 882 F/g at a current density of 1.0 A/g in a KOH electrolyte, and the specific capacitance retention of the MnO2/GF electrode can reach about 90.1% after 5000 charge-discharge cycles at a current density of 10 A/g. Furthermore, a MnO2/GF∥MnO2/GF symmetric supercapacitor device was fabricated with two pieces of MnO2/GF electrodes and ordinary filter paper with a 1 M KOH/PVA gel electrolyte as a separator. The single symmetric device displayed a high energy density of 64.2 Wh/kg at a power density of 400 W/kg within an applied voltage of 1.6 V, and this value was superior to those of previously reported MnO2-based systems. A tandem device consisting of a five-series tandem device (the applied voltage of a single device was 0.7 V) and a three-series tandem device (the applied voltage of a single device was 1.6 V) was prepared to drive a red light-emitting diode (LED). These findings open up application prospects for MnO2-based composite electrode materials for high-performance supercapacitors.

Electrochemically Effective Surface Area of a Polyaniline Nanowire-Based Platinum Microelectrode and Development of an Electrochemical DNA Sensor

Electrochemical DNA sensors based on nanocomposite materials of polyaniline nanowires (PANi NWs) have been published in the literature. However, it is interesting that there are very few research studies related to the development of electrochemical DNA sensors based on PANi NWs individually. In this study, PANi NWs were synthesized site-specifically on a Pt microelectrode with only 0.785 mm2 area using an electropolymerization procedure. The electrosynthesis allows direct deposition of PANi NWs onto the Pt microelectrode in a rapid and cost-effective way. The good properties of PANi NWs including uniform size, uniform distribution throughout the Pt working electrode, and H2SO4 doping which improved the conductivity of the PANi material were obtained. Especially, the electrochemically effective surface area of the PANi NW-based Pt microelectrode determined in this work is nearly 19 times larger than that of the Pt working electrode. The PANi NW layer with large electrochemically effective surface area and high biocompatibility is consistent with the application in electrochemical DNA sensors. The fabricated DNA sensors show advantages such as simple fabrication, direct detection, high sensitivity (with the detection limit of 2.48 × 10−14 M), good specificity, and low sample volume requirement. This study also contributes to confirm the role of PANi NWs in DNA probe immobilization as well as in electrochemical signal transmission in the development of electrochemical DNA sensors.

POM-derived MoO3/CoMoO4 mixed oxides directed by glucose for high-performance supercapacitors

Facile synthesis of MoO3/CoMoO4 composites derived from polyoxometalate using a sacrificial template for high performance supercapacitors.