Micromorphology-controlled synthesis of polypyrrole films by using binary surfactant of Span80/OP10 via interfacial polymerization and their enhanced electrochemical capacitance

Supercapacitors: An Efficient Way for Energy Storage Application

To date, batteries are the most widely used energy storage devices, fulfilling the requirements of different industrial and consumer applications. However, the efficient use of renewable energy sources and the emergence of wearable electronics has created the need for new requirements such as high-speed energy delivery, faster charge-discharge speeds, longer lifetimes, and reusability. This leads to the need for supercapacitors, which can be a good complement to batteries. However, one of their drawbacks is their lower energy storage capability, which has triggered worldwide research efforts to increase their energy density. With the introduction of novel nanostructured materials, hierarchical pore structures, hybrid devices combining these materials, and unconventional electrolytes, significant developments have been reported in the literature. This paper reviews the short history of the evolution of supercapacitors and the fundamental aspects of supercapacitors, positioning them among other energy-storage systems. The main electrochemical measurement methods used to characterize their energy storage features are discussed with a focus on their specific characteristics and limitations. High importance is given to the integral components of the supercapacitor cell, particularly to the electrode materials and the different types of electrolytes that determine the performance of the supercapacitor device (e.g., storage capability, power output, cycling stability). Current directions in the development of electrode materials, including carbonaceous forms, transition metal-based compounds, conducting polymers, and novel materials are discussed. The synergy between the electrode material and the current collector is a key factor, as well as the fine-tuning of the electrode material and electrolyte.

Synthesis and application of polypyrrole nanofibers: a review

State-of-the-art polypyrrole nanofiber-based nanoarchitectonics can be generally fabricated by electrospinning, interfacial polymerization and reactive template methods. Even though analogous nanofiber morphologies and nanofibrous network architectures can be obtained by these methods, the structural details and structural complexities may alter significantly as different synthesis methods are applied. For the electrospinning technique, on one hand, nanofibers can be directly obtained by spinning polypyrrole-containing dope solutions; on the other, the electrospun nanofiber mats can be used as templates to direct the nanofiber formation; a two-step fabrication process, including the electrospinning of polymer nanofiber mats and deposition of polypyrrole on the polymer nanofibers' surface, is generally employed. By tuning the electrospinning parameters, the composition, diameter, morphology, and alignment of the as-obtained electrospun nanofiber mat can be effectively controlled, which may allow the fabrication of polypyrrole nanofibers with sophisticated nanostructures and nanoarchitectures. Interfacial polymerization is capable of generating polypyrrole nanofibers without templates. It is speculated that the protonation and re-orientation of polypyrrole at the oil-water interface may decoil the polymer chains and transform them into more extended conformations, while the charged polymer chains more easily diffuse into the water phase and form a stable dispersion. Different from electrospinning, the reactive templates may drive the formation of polypyrrole nanofibers through either redox or protonation mechanisms. Nanofibers with different curvatures, compositions, and architectures can be obtained by using different types of reactive template in a simple, fast, environment-friendly and one-step manner. A wide range of applications have been demonstrated by the polypyrrole nanofiber-based nanoarchitectonics, including cell culture, tissue engineering, neural stimulation, energy storage, and organic electronics.

Interface-assisted synthesis: a gateway to effective nanostructure tuning of conducting polymers

The interface-assisted polymerization technique can be viewed as a powerful emerging tool for the synthesis of conducting polymers (CPs) on a large scale. Contrary to other bulk or single-phase polymerization techniques, interface-assisted synthesis strategies offer effective nanostructure control in a confined two-dimensional (2-D) space. This review focuses on the types of interfaces, mechanism at the interface, advantages and future perspectives of the interfacial polymerization in comparison to conventional polymerization techniques. Hence, the primary focus is on briefing the different types of the chemical methods of polymerization, followed by uniqueness in the reaction dynamics of interface polymerization. The classification of interfaces into four types (liquid/solid, gas/liquid, liquid/liquid, and gas/solid) is based on the versatility and underlying mechanistic pathway of the polymerization of each type. The role of interface in tuning the nanostructure of CPs and the performance evaluation of pristine CPs based on the electrical conductivity are also discussed. Finally, the future outlook of this emerging field is discussed and proposed in detail through some multifunctional applications of synthesized conducting polymers.

Tunable Three-Dimensional Nanostructured Conductive Polymer Hydrogels for Energy-Storage Applications

Three-dimensional (3D) nanostructured conducting polymer hydrogels represent a group of high-performance electrochemical energy-storage materials. Here, we demonstrate a molecular self-assembly approach toward controlled synthesis of nanostructured polypyrrole (PPy) conducting hydrogels, which was "cross-linked" by a conjugated dopant molecule trypan blue (TB) to form a 3D network with controlled morphology. The protonated TB by ion bonding aligns the free sulfonic acid groups into a certain spatial structure. The sulfonic acid group and the PPy chain are arranged by a self-sorting mechanism to form a PPy nanofiber structure by electrostatic interaction and hydrogen bonding. It is found that PPy hydrogels doped with varying dopant concentrations and changing dopant molecules exhibited controllable morphology and tunable electrochemical properties. In addition, the conjugated TB dopants promoted interchain charge transport, resulting in higher electrical conductivity (3.3 S/cm) and pseudocapacitance for the TB-doped PPy, compared with PPy synthesized without TB. When used as supercapacitor electrodes, the TB-doped PPy hydrogel reaches maximal specific capacitance of 649 F/g at the current density 1 A/g. The result shows that PPy nanostructured hydrogels can be tuned for potential applications in next-generation energy-storage materials.

Supercapacitor Energy Storage Device Using Biowastes: A Sustainable Approach to Green Energy

The demand for renewable energy sources worldwide has gained tremendous research attention over the past decades. Technologies such as wind and solar have been widely researched and reported in the literature. However, economical use of these technologies has not been widespread due partly to cost and the inability for service during of-source periods. To make these technologies more competitive, research into energy storage systems has intensified over the last few decades. The idea is to devise an energy storage system that allows for storage of electricity during lean hours at a relatively cheaper value and delivery later. Energy storage and delivery technologies such as supercapacitors can store and deliver energy at a very fast rate, offering high current in a short duration. The past decade has witnessed a rapid growth in research and development in supercapacitor technology. Several electrochemical properties of the electrode material and electrolyte have been reported in the literature. Supercapacitor electrode materials such as carbon and carbon-based materials have received increasing attention because of their high specific surface area, good electrical conductivity and excellent stability in harsh environments etc. In recent years, there has been an increasing interest in biomass-derived activated carbons as an electrode material for supercapacitor applications. The development of an alternative supercapacitor electrode material from biowaste serves two main purposes: (1) It helps with waste disposal; converting waste to a useful product, and (2) it provides an economic argument for the substantiality of supercapacitor technology. This article reviews recent developments in carbon and carbon-based materials derived from biowaste for supercapacitor technology. A comparison between the various storage mechanisms and electrochemical performance of electrodes derived from biowaste is presented.