Background, fundamental understanding and progress in electrochemical capacitors

High-Performance 3D Nanostructured Silver Electrode for Micro-Supercapacitor Application

In the current energy crisis scenario, the development of renewable energy forms such as energy storage systems among the supercapacitors is an urgent need as a tool for environmental protection against increasing pollution. In this work, we have designed a novel 3D nanostructured silver electrode through an antireplica/replica template-assisted procedure. The chemical surface and electrochemical properties of this novel 3D electrode have been studied in a 5 M KOH electrolyte. Microstructural characterization and compositional analysis were studied by SEM, energy-dispersive X-ray spectroscopy, XRD technique, and Kripton adsorption at -198 °C, together with cyclic voltammetry and galvanostatic charge-discharge cycling measurements, Coulombic efficiency, cycle stability, and their leakage current drops, in addition to the self-discharge and electrochromoactive behavior, were performed to fully characterize the 3D nanostructured electrode. Large areal capacitance value of 0.5 F/cm2 and Coulombic efficiency of 97.5% are obtained at a current density of 6.4 mA/cm2 for a voltage window of 1.2 V (between -0.5 and 0.8 V). The 3D nanostructured silver electrode exhibits excellent capacitance retention (95%) during more than 2600 cycles, indicating a good cyclic stability. Additionally, the electrode delivers a high energy density of around 385.87 μWh/cm2 and a power density value of 3.82 μW/cm2 and also displays an electrochromoactive behavior. These experimental results strongly support that this versatile combined fabrication procedure is a suitable strategy for improving the electrochemical performances of 3D nanostructured silver electrodes for applications as micro-supercapacitors or in electrochemical devices.

Nanostructured Conducting Polymers and Their Applications in Energy Storage Devices

Due to the energy requirements for various human activities, and the need for a substantial change in the energy matrix, it is important to research and design new materials that allow the availability of appropriate technologies. In this sense, together with proposals that advocate a reduction in the conversion, storage, and feeding of clean energies, such as fuel cells and electrochemical capacitors energy consumption, there is an approach that is based on the development of better applications for and batteries. An alternative to commonly used inorganic materials is conducting polymers (CP). Strategies based on the formation of composite materials and nanostructures allow outstanding performances in electrochemical energy storage devices such as those mentioned. Particularly, the nanostructuring of CP stands out because, in the last two decades, there has been an important evolution in the design of various types of nanostructures, with a strong focus on their synergistic combination with other types of materials. This bibliographic compilation reviews state of the art in this area, with a special focus on how nanostructured CP would contribute to the search for new materials for the development of energy storage devices, based mainly on the morphology they present and on their versatility to be combined with other materials, which allows notable improvements in aspects such as reduction in ionic diffusion trajectories and electronic transport, optimization of spaces for ion penetration, a greater number of electrochemically active sites and better stability in charge/discharge cycles.

Electrochemically Deposited MoS2 and MnS Multilayers on Nickel Substrates in Inverse Opal Structure as Supercapacitor Microelectrodes

High-dispersion polystyrene (PS) microspheres with monodispersity were successfully synthesized by the non-emulsification polymerization method, and three-dimensional (3D) photonic crystals of PS microspheres were fabricated by electrophoretic self-assembly (EPSA). The metal nickel inverse opal structure (IOS) photonic crystal, of which the structural thickness can be freely adjusted via electrochemical deposition (ECD), and subsequently, MnS/MoS₂/Ni-IOS specimens were also prepared by ECD. Excellent specific capacitance values (1880 F/g) were obtained at a charge current density of 5 A/g. The samples in this experiment were tested for 2000 cycles of cycle life and still retained a reasonably good level of 76.6% of their initial capacitance value. In this study, the inverse opal structure photonic crystal substrate was used as the starting point, and then the microelectrode material for the MnS/MoS₂/Ni-IOS supercapacitor was synthesized. Our findings show that the MnS/MoS₂/Ni-IOS microelectrode makes a viable technical contribution to the design and fabrication of high-performance supercapacitors.

Highly efficient ionic‐liquid based solid polymer electrolyte for energy device (RAFM 2022)

We have successfully synthesized highly conducting polymer electrolyte incorporated ionic liquid films. There was a rise in conductivity by ionic liquid doping which is clarified by impedance spectroscopy. Fourier transform infra red spectroscopy confirms complexation as well as composite nature. Polarized optical microscopy shows decrease in crysatllinity (more amorphous) by ionic liquid doping. Maximum conducting ionic liquid incorporated polymer electrolyte sandwitched between electrodes, used for fabricating electrical double layer capacitor (EDLC) and dye sensitized solar cell (DSSC) further affirm that these ionic liquid doped polymer electrolyte could be a novel alternative in electrochemical devices.

A Modular Strategy for Expanding Electron-Sink Capacity in Noncanonical Cluster Assemblies

A modular synthetic strategy is described whereby organometallic complexes exhibiting considerable electron-sink capacity may be assembled by using only a few simple molecular components. The Fe₂(PPh₂)₂(CO)₅ fragment was selected as a common electroactive component and was assembled around aromatic cores bearing one, two, or three isocyanide functional groups, with the resultant complexes possessing electron-sink capacities of two, four, and six electrons, respectively. The latter complex is noteworthy in that its electron-sink capacity was found to rival that of large multinuclear clusters (e.g., [Ni₃₂C₆(CO)₃₆]^6– and [Ni₃₈Pt₆(CO)₄₈]^6–), which are often considered as benchmarks of electron-sink behavior. Moreover, the modular assembly bearing three Fe₂(PPh₂)₂(CO)₅ fragments was observed to undergo reduction to a hexaanionic state over a potential window of about −1.4 to −2.1 V (vs Fc/Fc⁺), the relatively compressed range being attributed to potential inversions operative during the addition of the second, fourth, and sixth electrons. Such complexes may be designated noncanonical clusters because they exhibit redox properties similar to those of large multinuclear clusters yet lack the extensive network of metal–metal bonds and the condensed metallic cores that typify the latter.

By use of a modular synthetic strategy and relatively few molecular components, organometallic complexes exhibiting considerable electron-sink capacity have been characterized. Complexes bearing one, two, or three Fe₂(PPh₂)₂(CO)₅ fragments bound to aromatic isocyanide cores were found to possess electron-sink capacities of two, four, and six electrons, respectively, the latter rivaling the electron-sink capacity of large polynuclear cluster benchmarks.

Synthesis and electrochemical study of phosphorus-doped porous carbon for supercapacitor applications

In the present investigation, we report the incorporation of phosphorous (P) atoms in the activated carbon and study its effect on the electrochemical performance. Porous carbon is synthesized by the chemical activation method from a bioresource and then pretreated with nitric acid. Phosphorus atoms were doped by the simple chemical method. The obtained phosphorous-doped nano-materials show an appreciable change of porosity and creation of a more wide range of meso- and macropores, and this affects their adsorption and electrochemical performance. The electrochemical study shows that doped carbon obtained at 850 °C (ACtP-850) delivers the maximum specific capacitance (328 Fg−1) in neutral aqueous electrolyte (1 M Na2SO4). The doped carbon material not only exhibits good cycling performance but also the highest specific energy of 29 Wh kg−1 corresponding to a specific power of 646 W kg−1. The improved capacitive performance of phosphorous-doped porous carbon material proposes its use in energy storage applications.

Enhanced electrochemical performance of hierarchical porous carbon/polyaniline composite for supercapacitor applications

In this work, activated carbon/polyaniline (AC/PANi) composites were synthesized by low temperature in situ polymerization and their electrochemical performance was investigated. Microstructure and morphology examination of the samples confirmed a uniform coating of polyaniline on AC surfaces without any change in the structure. The electrochemical studies of the samples confirmed the improvement in the electrochemical performance of AC/PANi composites. Despite a decrease in the specific surface area a substantial increase in electrochemical performance is recorded for the AC/PANi composites due to the synergistic effect between the pseudocapacitance and double layer capacitance. The highest specific capacitance of 1021 F g−1 was calculated for the APA-29.4 composite in neutral aqueous electrolyte (1 M Na2SO4) which is many times greater than the specific capacitance values for AC (253 F g−1) and PANi (389 F g−1). The enhancement in the electrochemical performance of AC after polymerization with PANi in composites favours its use as a favourable electrode material for the energy storage devices.