Intrinsically Conducting Polymer Composites as Active Masses in Supercapacitors

Modified Working Electrodes for Organic Electrosynthesis

Organic electrosynthesis has gained much attention over the last few decades as a promising alternative to traditional synthesis methods. Electrochemical approaches offer numerous advantages over traditional organic synthesis procedures. One of the most interesting aspects of electroorganic synthesis is the ability to tune many parameters to affect the outcome of the reaction of interest. One such parameter is the composition of the working electrode. By changing the electrode material, one can influence the selectivity, product distribution, and rate of organic reactions. In this Review, we describe several electrode materials and modifications with applications in organic electrosynthetic transformations. Included in this discussion are modifications of electrodes with nanoparticles, composite materials, polymers, organic frameworks, and surface-bound mediators. We first discuss the important physicochemical and electrochemical properties of each material. Then, we briefly summarize several relevant examples of each class of electrodes, with the goal of providing readers with a catalog of electrode materials for a wide variety of organic syntheses.

An anticoagulant supercapacitor for implantable applications

With the rapid advancement of implantable electronic medical devices, implantable supercapacitors have emerged as popular energy storage devices. However, supercapacitors inevitably come into direct contact with blood when implanted, potentially causing adverse clinical reactions such as coagulation and thrombosis, impairing the performance of implanted energy storage devices, and posing a serious threat to human health. Therefore, this work aims to design an anticoagulant supercapacitor by heparin doped poly(3, 4-ethylenedioxythiophene) (PEDOT) for possible applications in implantable bioelectronics. Heparin (Hep), the as-known anticoagulant macromolecule acts as the counterion for PEDOT doping to enhance its conductivity, and the bioelectrode material PEDOT: Hep with anticoagulant activity is synthesized via chemical oxidation polymerization. Concurrently, the anticoagulant supercapacitor is constructed through in-situ polymerization, where PEDOT: Hep and bacterial cellulose as electrode material and electrolyte layer, respectively. Owing to the incorporation of heparin, the supercapacitor exhibits high hemocompatibility with hemolysis rate <5 %, good anticoagulant performance with coagulation time of 63.4 s, reasonable cycle stability with capacitance retention rate of 76.24 % after 20, 000 cycles, and supplies power for implanted heart rate sensors in female mice. This work provides a platform for implantable electronics to achieve anticoagulant activity in vivo.

Electro-Co-Polymerisation of Polypyrrole-Polyaniline Composites in Ionic Liquids for Metal-Free Hydrogen Evolution Electrodes

Pure organic films consisting of polypyrrole, polyaniline and a composite of polypyrrole and polyaniline electrodeposited in the ionic liquid EMIM-TFSI onto mesoporous carbon electrodes are tested for their hydrogen evolution reaction capabilities. The use of these intrinsically conducting polymers is seen as a way of stepping away from expensive and rare metallic catalysts. Co-polymerisation of polypyrrole and polyaniline in a 1 : 10 ratio in EMIM-TFSI was found to be doped with the TFSI- anion and be much more active to the hydrogen evolution reaction when compared to pure polymers. Tafel analysis of the composite gave a value of 144 mV/dec indicating that the Volmer step is the rate limiting step. However, stability tests showed an improvement in the composite's overpoential performance for the hydrogen evolution reaction.

In-Situ Coating of Iron with a Conducting Polymer, Polypyrrole, as a Promise for Corrosion Protection

Iron microparticles were coated with polypyrrole in situ during the chemical oxidation of pyrrole with ammonium peroxydisulfate in aqueous medium. A series of hybrid organic/inorganic core-shell materials were prepared with 30-76 wt% iron content. Polypyrrole coating was revealed by scanning electron microscopy, and its molecular structure and completeness were proved by FTIR and Raman spectroscopies. The composites of polypyrrole/carbonyl iron were obtained as powders and characterized with respect to their electrical properties. Their resistivity was monitored by the four-point van der Pauw method under 0.01-10 MPa pressure. In an apparent paradox, the resistivity of composites increased from the units Ω cm for neat polypyrrole to thousands Ω cm for the highest iron content despite the high conductivity of iron. This means that composite conductivity is controlled by the electrical properties of the polypyrrole matrix. The change of sample size during the compression was also recorded and provides a parameter reflecting the mechanical properties of composites. In addition to conductivity, the composites displayed magnetic properties afforded by the presence of iron. The study also illustrates the feasibility of the polypyrrole coating on macroscopic objects, demonstrated by an iron nail, and offers potential application in the corrosion protection of iron. The differences in the morphology of micro- and macroscopic polypyrrole objects are described.

Flexible Sensors Based on Conductive Polymer Composites

Elastic polymer-based conductive composites (EPCCs) are of great potential in the field of flexible sensors due to the advantages of designable functionality and thermal and chemical stability. As one of the popular choices for sensor electrodes and sensitive materials, considerable progress in EPCCs used in sensors has been made in recent years. In this review, we introduce the types and the conductive mechanisms of EPCCs. Furthermore, the recent advances in the application of EPCCs to sensors are also summarized. This review will provide guidance for the design and optimization of EPCCs and offer more possibilities for the development and application of flexible sensors.

Recent advances in food waste-derived nanoporous carbon for energy storage

Affordable and environmentally friendly electrochemically active raw energy storage materials are in high demand to switch to mass-scale renewable energy. One particularly promising avenue is the feasibility of utilizing food waste-derived nanoporous carbon. This material holds significance due to its widespread availability, affordability, ease of processing, and, notably, its cost-free nature. Over the years, various strategies have been developed to convert different food wastes into nanoporous carbon materials with enhanced electrochemical properties. The electrochemical performance of these materials is influenced by both intrinsic factors, such as the composition of elements derived from the original food sources and recipes, and extrinsic factors, including the conditions during pyrolysis and activation. While current efforts are dedicated to optimizing process parameters to achieve superior performance in electrochemical energy storage devices, it is timely to take stock of the current state of research in this emerging field. This review provides a comprehensive overview of recent developments in the fabrication and surface characterisation of porous carbons from different food wastes. A special focus is given on the applications of these food waste derived porous carbons for energy storage applications including batteries and supercapacitors.

Developments in conducting polymer-, metal oxide-, and carbon nanotube-based composite electrode materials for supercapacitors: a review

Supercapacitors are the latest development in the field of energy storage devices (ESDs). A lot of research has been done in the last few decades to increase the performance of supercapacitors. The electrodes of supercapacitors are modified by composite materials based on conducting polymers, metal oxide nanoparticles, metal-organic frameworks, covalent organic frameworks, MXenes, chalcogenides, carbon nanotubes (CNTs), etc. In comparison to rechargeable batteries, supercapacitors have advantages such as quick charging and high power density. This review is focused on the progress in the development of electrode materials for supercapacitors using composite materials based on conducting polymers, graphene, metal oxide nanoparticles/nanofibres, and CNTs. Moreover, we investigated different types of ESDs as well as their electrochemical energy storage mechanisms and kinetic aspects. We have also discussed the classification of different types of SCs; advantages and drawbacks of SCs and other ESDs; and the use of nanofibres, carbon, CNTs, graphene, metal oxide-nanofibres, and conducting polymers as electrode materials for SCs. Furthermore, modifications in the development of different types of SCs such as pseudo-capacitors, hybrid capacitors, and electrical double-layer capacitors are discussed in detail; both electrolyte-based and electrolyte-free supercapacitors are taken into consideration. This review will help in designing and fabricating high-performance supercapacitors with high energy density and power output, which will act as an alternative to Li-ion batteries in the future.

Enhancing supercapacitor performance of Ni-Co-Mn metal-organic frameworks by compositing it with polyaniline and reduced graphene oxide

Metal-organic frameworks (MOFs) are one of the most sought-after materials in the domain of supercapacitors and can be tailored to accommodate diverse compositions, making them amenable to facile functionalization. However, their intrinsic specific capacitance as well as energy density is minimal, which hinders their usage for advanced energy storage applications. Therefore, herein, we have prepared six electrodes, i.e., Ni-Co-Mn MOFs, polyaniline (PANI), and reduced graphene oxide (rGO) along with their novel nanocomposites, i.e., C1, C2, and C3, comprising MOFs : PANI : rGO in a mass ratio of 100 : 1 : 0.5, 100 : 1 : 1, and 100 : 1 : 10, respectively. The polyaniline conducting polymer and rGO enabled efficient electron transport, enhanced charge storage processes, substantial surface area facilitating higher loading of active materials, promoting electrochemical reactions, and ultimately enhanced nanocomposite system performance. As a result, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques confirmed the successful synthesis and revealed distinct morphological features of the materials. Following electrochemical testing, it was observed that composition C2 exhibited the highest performance, demonstrating a groundbreaking specific capacitance of 1007 F g-1 at 1 A g-1. The device showed a good energy density of 25.11 W h kg-1 and a power density of 860 W kg-1. Remarkably, the device demonstrated a capacity retention of 115% after 1500 cycles, which is a clear indication of the wettability factor, according to the literature. The power law indicated b-values in a range of 0.58-0.64, verifying the hybrid-type behavior of supercapacitors.

Conducting and Magnetic Hybrid Polypyrrole/Nickel Composites and Their Application in Magnetorheology

Hybrid organic/inorganic conducting and magnetic composites of core-shell type have been prepared by in-situ coating of nickel microparticles with polypyrrole. Three series of syntheses have been made. In the first, pyrrole was oxidised with ammonium peroxydisulfate in water in the presence of various amounts of nickel and the composites contained up to 83 wt% of this metal. The second series used 0.1 M sulfuric acid as a reaction medium. Finally, the composites with polypyrrole nanotubes were prepared in water in the presence of structure-guiding methyl orange dye. The nanotubes have always been accompanied by the globular morphology. FTIR and Raman spectroscopies confirmed the formation of polypyrrole. The resistivity of composite powders of the order of tens to hundreds Ω cm was monitored as a function of pressure up to 10 MPa. The resistivity of composites slightly increased with increasing content of nickel. This apparent paradox is explained by the coating of nickel particles with polypyrrole, which prevents their contact and subsequent generation of metallic conducting pathways. Electrical properties were practically independent of the way of composite preparation or nickel content and were controlled by the polypyrrole phase. On the contrary, magnetic properties were determined exclusively by nickel content. The composites were used as a solid phase to prepare a magnetorheological fluid. The test showed better performance when compared with a different nickel system reported earlier.

Ag(e)ing and Degradation of Supercapacitors: Causes, Mechanisms, Models and Countermeasures

The most prominent and highly visible advantage attributed to supercapacitors of any type and application, beyond their most notable feature of high current capability, is their high stability in terms of lifetime, number of possible charge/discharge cycles or other stability-related properties. Unfortunately, actual devices show more or less pronounced deterioration of performance parameters during time and use. Causes for this in the material and component levels, as well as on the device level, have only been addressed and discussed infrequently in published reports. The present review attempts a complete coverage on these levels; it adds in modelling approaches and provides suggestions for slowing down ag(e)ing and degradation.

Carbonized Leather Waste: A Review and Conductivity Outlook

The carbonization of collagen-based leather waste to nitrogen-containing carbon is reviewed with respect to the preparation, characterization of carbonized products, and applications proposed in the literature. The resulting nitrogen-containing carbons with fibrous morphology have been used as adsorbents in water pollution treatment, in electrocatalysis, and especially in electrodes of energy-storage devices, such as supercapacitors and batteries. Although electrical conductivity has been implicitly exploited in many cases, the quantitative determination of this parameter has been addressed in the literature only marginally. In this report, attention has been newly paid to the determination of conductivity and its dependence on carbonization temperature. The resulting powders cannot be compressed into pellets for routine conductivity determination. A new method has been used to follow the resistivity of powders as a function of pressure up to 10 MPa. The conductivity at this pressure increased from 9.4 × 10^-8 S cm^-1 for carbonization at 500 °C to 5.3 S cm^-1 at 1000 °C. The conductivity of the last sample was comparable with conducting polymers such as polypyrrole. The carbonized leather thus has the potential to be used in applications requiring electrical conduction.