Recent Advances in the Tunable Optoelectromagnetic Properties of PEDOTs

Conducting polymers represent a crucial class of functional materials with widespread applications in diverse fields. Among these, poly(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives have garnered significant attention due to their distinctive optical, electronic, and magnetic properties, as well as their exceptional tunability. These properties often exhibit intricate interdependencies, manifesting as synergistic, concomitant, or antagonistic relationships. In optics, PEDOTs are renowned for their high transparency and unique photoelectric responses. From an electrical perspective, they display exceptional conductivity, thermoelectric, and piezoelectric performance, along with notable electrochemical activity and stability, enabling a wide array of electronic applications. In terms of magnetic properties, PEDOTs demonstrate outstanding electromagnetic shielding efficiency and microwave absorption capabilities. Moreover, these properties can be precisely tailored through molecular structure modifications, chemical doping, and composite formation to suit various application requirements. This review systematically examines the mechanisms underlying the optoelectromagnetic properties of PEDOTs, highlights their tunability, and outlines prospective research directions. By providing critical theoretical insights and technical references, this review aims to advance the application landscape of PEDOTs.

Mini Review of Reliable Fabrication of Electrode under Stretching for Supercapacitor Application

Currently, there is an increasing demand for portable and wearable electronics. This has necessitated the development of stretchable energy storage devices, while simultaneously maintaining performance. Hence, the electrodes and electrolyte materials used in stretchable supercapacitors should be robust under severe mechanical deformation. Polymers are widely used in the fabrication of stretchable supercapacitors. It is not only crucial to choose good polymer candidates with inherent advantages, but it is also important to design suitable polymer materials for both electrodes and electrolytes. This mini-review explains the concept of stretchable supercapacitors, the theoretical background of polymer-based electrodes for supercapacitors, and the fabrication strategies of stretchable electrodes for supercapacitors. Finally, we present the drawbacks and areas that still need to be developed.

A Biodegradable Polymer-Based Plastic Chip Electrode as a Current Collector in Supercapacitor Application

Here, we report the performance of a biodegradable polymer-based Plastic chip Electrode (PCE) as a current collector in supercapacitor applications. Its production was evaluated using two redox materials (conducting polymers polyaniline and poly(3,4-ethylene dioxythiophene)) and a layered material, rGO. The conducting polymers were directly deposited over the Eco-friendly PCE (EPCE) using the galvanostatic method. The rGO was prepared in the conventional way and loaded over the EPCE using a binder. Both conducting polymers and rGO showed proper specific capacitance compared to previous studies with regular current collectors. Electrodes were found highly stable during experiments in high acidic medium. The supercapacitive performance was evaluated with cyclic voltammetry, charge–discharge measurements, and impedance spectroscopy. The supercapacitive materials were also characterized for their electrical and microscopic properties. Polyaniline and PEDOT were deposited over EPCEs showing >150 Fg−1 and >120 Fg−1 specific capacitance, respectively, at 0.5 Ag−1. rGO continued to show higher particular capacitance of >250 Fg−1 with excellent charge–discharge cyclic stability. The study concludes that EPCs can be used as promising electrodes for electrical energy storage applications.

Conjugated Polyelectrolytes: Underexplored Materials for Pseudocapacitive Energy Storage

Conjugated polyelectrolytes (CPEs) are characterized by an electronically delocalized backbone bearing ionic functionalities. These features lead to properties relevant for use in energy-storing pseudocapacitor devices, including ionic conductivity, water processability, gel-formation, and formation of polaronic species stabilized by electrostatic interactions. In this Perspective, the basis for evaluating the figures of merit for pseudocapacitors is provided, together with the techniques used for their evaluation. The general utility and challenges encountered with neutral conjugated polymers are then discussed. Finally, recent advances on the use of CPEs in pseudocapacitor devices are reviewed. The article is concluded by discussing how their miscibility in aqueous media permits the incorporation of CPEs in living materials that are capable of switching function from extraction of energy from bacterial metabolic pathways to pseudocapacitor energy storage.

Regulating monomer assembly to enhance PEDOT capacitance performance via different oxidants

The development of poly(3,4-ethylenedioxythiophene) (PEDOT) with high specific capacitance is the key to pursuing high-performance supercapacitors, and the electrochemical properties of PEDOT are closely related to the oxidation degree and conjugated chain length of its molecular chain. In this work, the influences of various oxidants (FeCl₃, Fe(Tos)₃ and MoCl₅) on the molecular chain structure and capacitive properties of PEDOT via vapor phase polymerization were systematically investigated. Fe(Tos)₃ can significantly improve the degree of oxidation and the length of the conjugated chain of PEDOT compared to FeCl₃ and MoCl₅, enhancing the conductivity and providing more active sites for Faraday reaction. Therefore, the PEDOT/P(Fe(Tos)₃) electrode displays a considerable conductivity of 73 S cm^-1, high areal capacitance (419 mF cm^-2) and excellent electrochemical stability under the different bent state. Moreover, the conjugated structure strengthens the interaction between PEDOT chains, achieving good cycle stability. Therefore, Fe(Tos)₃ is an ideal oxidant for obtaining high-performance PEDOT electrode materials.

Benchmarking the Performance of Electropolymerized Poly(3,4-ethylenedioxythiophene) Electrodes for Neural Interfacing

The development of electronics adept at interfacing with the nervous system is an ever-growing effort, leading to discoveries in fundamental neuroscience applied in clinical setting. Highly capacitive and electrochemically stable electronic materials are paramount for these advances. A systematic study is presented where copolymers based on 3,4-ethylenedioxythiophene (EDOT) and its hydroxyl-terminated counterpart (EDOTOH) are electropolymerized in an aqueous solution in the presence of various counter anions and additives. Amongst the conducting materials developed, the copolymer p(EDOT-ran-EDOTOH) doped with perchlorate in the presence of ethylene glycol shows high specific capacitance (105 F g^-1 ), and capacitance retention (85%) over 1000 galvanostatic charge-discharge cycles. A microelectrode array-based on this material is fabricated and primary cortical neurons are cultured therein for several days. The microelectrodes electrically stimulate targeted neuronal networks and record their activity with high signal-to-noise ratio. The stability of charge injection capacity of the material is validated via long-term pulsing experiments. While providing insights on the effect of additives and dopants on the electrochemical performance and operational stability of electropolymerized conducting polymers, this study highlights the importance of high capacitance accompanied with stability to achieve high performance electrodes for biological interfacing.

Oxidative Spin-Spray-Assembled Coordinative Multilayers as Platforms for Capacitive Films

The spin-spray-assisted layer-by-layer (LbL) assembly technique was used to prepare coordinative oxidative multilayers from Ce(IV), inorganic polyphosphate (PP), and graphene oxide (GO). The films consist of successive tetralayers and have a general structure (PP/Ce/GO/Ce)n. Such oxidative multilayers have been shown to be a general platform for the electrodeless generation of conducting polymer and melanin-type films. Although the incorporation of GO enhances the film growth, the conventional dip LbL method is very time consuming. We show that the spin-spray method reduces the time required to grow thick multilayers by the order of magnitude and the film growth is linear from the beginning, which implies a stratified structure. We have deposited poly(3,4-ethylenedioxothiophene), PEDOT, on the oxidative multilayers and studied these redox-active films as models for melanin-type capacitive layers for supercapacitors to be used in biodegradable electronics, both before and after the electrochemical reduction of GO to rGO. The amount of oxidant and PEDOT scales linearly with the film thickness, and the charge transfer kinetics is not mass transfer-limited, especially after the reduction of GO. The areal capacitance of the films grows linearly with the film thickness, reaching a value of ca. 1.6 mF cm-2 with 20 tetralayers, and the specific volumetric (per film volume) and mass (per mass of PEDOT) capacitances are ca. 130 F cm-3 and 65 F g-1, respectively. 5,6-Dihydroxyindole can also be polymerized to a redox-active melanin-type film on these oxidative multilayers, with even higher areal capacitance values.

A Review of Supercapacitors Based on Graphene and Redox-Active Organic Materials

Supercapacitors are a highly promising class of energy storage devices due to their high power density and long life cycle. Conducting polymers (CPs) and organic molecules are potential candidates for improving supercapacitor electrodes due to their low cost, large specific pseudocapacitance and facile synthesis methods. Graphene, with its unique two-dimensional structure, shows high electrical conductivity, large specific surface area and outstanding mechanical properties, which makes it an excellent material for lithium ion batteries, fuel cells and supercapacitors. The combination of CPs and graphene as electrode material is expected to boost the properties of supercapacitors. In this review, we summarize recent reports on three different CP/graphene composites as electrode materials for supercapacitors, discussing synthesis and electrochemical performance. Novel flexible and wearable devices based on CP/graphene composites are introduced and discussed, with an eye to recent developments and challenges for future research directions.

PEDOT-based composites as electrode materials for supercapacitors

Poly (3, 4-ethylenedioxythiophene) (denoted PEDOT) already has a brief history of being used as an active material in supercapacitors. It has many advantages such as low-cost, flexibility, and good electrical conductivity and pseudocapacitance. However, the major drawback is low stability, which means an obvious capacitance drop after a certain number of charge-discharge cycles. Another disadvantage is its limited capacitance and this becomes an issue for industrial applications. To solve these problems, there are several approaches including the addition of conducting nanofillers to increase conductivity, and mixing or depositing metal oxide to enhance capacitance. Furthermore, expanding the surface area of PEDOT is one of the main methods to improve its performance in energy storage applications through special processes; for example using a three-dimensional substrate or preparing PEDOT aerogel through freeze drying. This paper reviews recent techniques and outcomes of PEDOT based composites for supercapacitors, as well as detailed calculations about capacitances. Finally, this paper outlines the new direction and recent challenges of PEDOT based composites for supercapacitor applications.