Enhanced electrochemical performances of polypyrrole/carboxyl graphene/carbon nanotubes ternary composite for supercapacitors

Self-Powered Sensors Made with Fabric-Based Electrodes and a Conductive Coating

Amidst the growing challenge of meeting global energy demands with conventional sources, self-powered devices offer promising solution. Flexible and stretchable electronics are pivotal in wearable technology, enhancing the scope and functionality of these devices. This study employs potassium sodium niobite-lithium antimonate (K0.5Na0.5NbO3-LiSbO3) nanoparticles as fillers in polyvinylidene fluoride (PVDF) to fabricate piezoelectric thin films. These films are integrated with fabric-based electrodes to develop high-performance, flexible self-powered sensors. The sensor comprises a fabric-based electrode with polypyrrole (PPy) coated on plain nylon fabric, a 0.93KNN-0.07LS/PVDF composite piezoelectric thin film, and a protective PET layer. Results demonstrate that the 0.93KNN-0.07LS/PVDF-PPy/nylon composite sensors exhibit a stable piezoelectric output. Under 6 Hz and 10 N excitation, the piezoelectric output reaches approximately 6.1 V upon pressing. Additionally, the device shows good linear sensitivity in the 2-20 N pressure range and produces clear, regular output waveforms under cyclic pressures of varying frequencies and amplitudes, indicating excellent response repeatability. Even after extensive bending, twisting, and 5000 pressing cycles, the sensors maintain considerable cyclic stability, demonstrating high durability. These tests collectively indicate that the developed sensors possess high sensitivity, flexibility, durability, stability, and significant self-powered potential. This research provides a reference for the next generation of textile-based electrodes and offers potential strategies for flexible, wearable applications.

A novel catalyst derived from Co-ZIFs to grow N-doped carbon nanotubes for all-solid-state supercapacitors with high performance

Carbon nanotubes (CNTs) have been widely used as electrode materials for electrochemical energy storage devices (e.g., supercapacitors) due to their excellent chemical and physical properties. However, conventional approaches (e.g., electron-beam vapor deposition and atomic layer deposition) to fabricate catalysts for the growth of CNTs are complex and demand high energy consumption. Herein, we report a facile method to synthesize catalysts derived from cobalt-containing zeolitic imidazolate frameworks (Co-ZIFs), which is exploited to in situ construct the three-dimensional (3D) CNT hybrid materials for all-solid-state supercapacitors. In brief, Co-ZIFs with a controllable structure is first grown on the inner porous surface of carbon foams pyrolyzed from commercial melamine foams, followed by thermal annealing and chemical vapor deposition to grow CNTs, achieving 3D free-standing CNT-based hybrids. The well-distributed Co-ZIFs in the carbon foam enable the grown CNTs with uniform structures and morphologies. Using the fabricated CNT-based hybrid as electrodes, the assembled all-solid-state supercapacitors show a high specific capacitance of 19.4 mF cm-2 at a current density of 0.5 mA cm-2, which could be further optimized to as high as 871.8 mF cm-2 by incorporating the pseudocapacitive material of manganese dioxide in CNT-based hybrids. This study provides a facile solution approach to fabricate the catalyst for the growth of a CNT inner porous substrate; the resultant 3D free-standing hybrids could be used as efficient electrodes for high-performance energy storage devices beyond supercapacitors.

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.

A light-fostered supercapacitor performance of multi-layered ReS2 grown on conducting substrates

The light-fostered supercapacitor performance introduces a new realm in the field of smart energy storage applications. Transition metal dichalcogenides (TMDCs) with direct band gap are intriguing candidates for developing a light-induced supercapacitor that can enhance energy storage when shined with light. Many TMDCs show a transition from a direct to indirect band gap as the layer number increases, while ReS2 possesses a direct band gap in both bulk and monolayer forms. The growth of such multi-layered 2D materials with high surface area on conducting substrates makes them suitable for smart energy storage applications with the ability to tune their performance with light irradiation. In this report, we present the growth of vertically aligned multi-layered ReS2 with large areal coverage on various conducting and non-conducting substrates, including stainless steel via chemical vapor deposition (CVD). To investigate the effect of light illumination on the charge storage performance, electrochemical measurements have been performed in dark and light conditions. Cyclic voltammetry (CV) curves showed an increase in the area enclosed by the curve, manifesting the increased charge storage capacity under light illumination as compared to dark. The volumetric capacitance value calculated from charging-discharging curves has increased from 17.9 F cm-3 to 29.8 F cm-3 with the irradiation of light for the as-grown ReS2 on a stainless steel plate. More than 1.5 times the capacitance enhancement is attributed to excess electron-hole pairs generated upon light illumination, contributing to the charge storage in the presence of light. The electrochemical impedance spectroscopy further augments these results. The high cyclic stability is attained with a capacitance retention value of 81% even after 10 000 repeated charging-discharging cycles.

Effect of graphene oxide with different morphological characteristics on properties of immobilized enzyme in the covalent method

Although graphene oxide (GO) has great potential in the field of immobilized enzyme catalysts, the detailed effects of GO with different morphological structures on immobilized enzyme are not well understood. GOs were prepared from 8000 mesh and nanoscale graphite at different reaction temperatures, and used as carriers to immobilize alpha-amylase by cross-linking method. The properties of GOs were characterized through Atomic force microscope, Fourier-transformed infrared, X-ray photoelectron spectroscopy, Raman and UV-Vis. Furthermore, the dosage of cross-linking agent, cross-linking time, optimum temperature/pH, thermal/pH/storage stability, reusability and kinetic parameters of immobilized enzymes were investigated. The results showed that the loading of alpha-amylase on GOs was 162.3-274.2 mg g^-1. The reusability experiments revealed high activity maintenance of immobilized alpha-amylase even after seven reaction cycles. Moreover, the storage stability of immobilized enzyme improved via immobilization in comparison with free one and it maintained over 70% of their initial activity after 20 days storage at 4 °C.

A Universal Electrolyte Formulation for the Electrodeposition of Pristine Carbon and Polypyrrole Composites for Supercapacitors

Electrodeposition of conducting polymer-carbon composites from an electrolyte precursor solution is a facile one-step approach to fabricate device-ready electrodes for energy storage. A key challenge in this approach is the dispersion of the carbon nanomaterials with the aqueous precursor solution with previous approaches either heavily oxidizing the carbon nanomaterials or using high concentrations of anionic surfactants as dopants. However, the former reduces the electrical conductivity of carbon, while the latter reduces the ionic mobility of the conducting polymer due to the large anion size. Herein, for the first time we present a quaternary electrolyte formulation for the fabrication of pristine carbon and polypyrrole (PPy) composites that does not sacrifice either electron or ion mobility. The electrolyte uses lithium perchlorate (20 mM) as a supporting electrolyte and dopant, sodium dodecylbenzenesulfonate at a very low concentration (1.43 mM) as a surfactant, together with pristine carbon nanomaterials and pyrrole monomers. The order of magnitude difference between the concentration of the dopant and surfactant ion allows the as-deposited PPy to be doped predominantly by small-sized and mobile perchlorate anions. Composites of PPy with carbon black, carbon nanotubes, and electrochemical exfoliated graphene (EEG) have been successfully prepared using this new quaternary electrolyte. The as-fabricated PPy/EEG composite electrodes showed a specific capacitance of 348.8 F g^-1 with a high rate capability (190.7 F g^-1 at 71 A g^-1). Supercapacitor devices based on the PPy/EEG composite electrodes exhibit a high rate behavior up to 500 mV s^-1 and a long cycle life of 5000 cycles.

The design of CNTs@Ni1/3Co2/3(CO3)1/2(OH)·0.11H2O in situ compounded in the nanoscale for all-solid-state supercapacitors

Ni_1/3Co_2/3(CO₃)_1/2(OH)·0.11H₂O (NCC) was in situ constructed on the surface of CNTs, which realized the nanoscale recombination of NCC and CNTs.

Investigations of structural, spectral and electronic properties of enrofloxacin and boron complexes via quantum chemical calculation and molecular docking

Quantum chemical analyses were performed over enrofloxacin and boron complexes. The most stable isomer of enrofloxacin was examined at M062X/6-31+G(d) level in gas phase. Structural and spectral characterizations of enrofloxacin and its complexes were performed at same level of theory. MEP maps of studied compound were calculated via ESP charges analyses. Some quantum chemical descriptors (QCDs) were calculated to determine the non-linear optical (NLO) and biological reactivity of studied molecules. Furthermore, molecular docking calculations between boron complexes and a protein (ID: 2ITN and 2ITV) were done. ADME analyses were done in the determination of the best drug candidate. As a result, complex (3) was found as the best in the NLO applications and it was found that complex (1) and (3) have similar biological reactivity in lung cancer treatment.

Polypyrrole nanotubes for electrochemically controlled extraction of atrazine, caffeine and progesterone

Polypyrrole (PPy) was electrochemically synthesized with charge control on the surface of a steel mesh. Two different morphologies (globular and nanotubular) were created and characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The modified electrodes were used as extraction phases in solid-phase extraction (SPE) and electrochemically controlled solid-phase extraction (EC-SPE) of atrazine, caffeine and progesterone. Raman spectroscopy was employed for the structural characterization of PPy after long exposure to the analytes. The electrochemical behavior was studied by cyclic voltammetry which revealed the higher capacitive behavior of polypyrrole nanotubes because of the huge superficial area, also no electrocatalytical behavior was observed evidencing the strong adsorption of the analytes on the PPy surface. The effects of the PPy oxidation state on the extraction performance were evaluated by in-situ electrochemical sorption experiments. The sorption capacity was evaluated by gas chromatography coupled to mass spectrometry (GC-MS). The method displays good stability, repeatability and reproducibility. The limits of detection range between 1.7-16.7 μg L^-1. Following the extraction of river water samples, it was possible to identify the presence of other endogenous organic compounds besides the analytes of interest. This indicates the potential of the method and material developed in this work. Graphical abstract Schematic representation of a steel mesh electrode covered with polypyrrole nanotubes used as extraction phase for separation of contaminants from aqueous samples. The oxidation level of polypyrrole was electrochemically tuned by which the adsorption of analytes is deeply affected.