A High-Energy Asymmetric Supercapacitor Based on Tomato-Leaf-Derived Hierarchical Porous Activated Carbon and Electrochemically Deposited Polyaniline Electrodes for Battery-Free Heart-Pulse-Rate Monitoring.

A simple and scalable method to fabricate a novel high-energy asymmetric supercapacitor using tomato-leaf-derived hierarchical porous activated carbon (TAC) and electrochemically deposited polyaniline (PANI) for a battery-free heart-pulse-rate monitor is reported. In this study, TAC is prepared by simple pyrolysis, exhibiting nanosheet-type morphology and a high specific surface area of ≈1440 m2 g-1 , and PANI is electrochemically deposited onto carbon cloth. The TAC- and PANI- based asymmetric supercapacitor demonstrates an electrochemical performance superior to that of symmetric supercapacitors, delivering a high specific capacitance of 248 mF cm-2 at a current density of 1.0 mA cm-2 . The developed asymmetric supercapacitor shows a high energy density of 270 µWh cm-2 at a power density of 1400 µW cm-2 , as well as an excellent cyclic stability of ≈95% capacitance retention after 10 000 charging-discharging cycles while maintaining ≈98% Coulombic efficiency. Impressively, the series-connected asymmetric supercapacitors can operate a battery-free heart-pulse-rate monitor extremely efficiently upon solar-panel charging under regular laboratory illumination.

Designing High-Performing Symmetric Supercapacitor by Engineering Polyaniline on Steel Mesh Surface via Electrodeposition.

Energy storage is one of the most stimulating requirements to keep civilization on the wheel of progress. Supercapacitors generally exhibit a high-power density, have a maximum life cycle, quick charging time, and are eco-friendly. Polyaniline (PANI), a conductive polymer, is considered an efficacious electrode material for supercapacitors due to its good electroactivity, including pseudocapacitive behavior. Here, we present the fabrication of a symmetric supercapacitor device based on steel mesh electrodeposited with PANI. Due to its effective conductivity, porous nature, and low cost, steel mesh is a good choice as a current collector to fabricate a high-performance supercapacitor at a low cost. The optimum fabricated supercapacitor has a high specific capacitance of ∼353 mF cm-2 . Furthermore, the supercapacitor obtained an energy density of ∼26.4 µW h cm-2 at a power density of ∼400 µW cm-2 . The fabricated supercapacitor shows high stability, as the initial capacitance remained almost the same after 1000 charge/discharge cycles. PANI is a promising candidate for mass production and wide applications due to its low cost and high performance.

Water-based Formuation of Inkjet Inks Using Jute Stick-derived Submicron Carbon Particles.

Biomass pyrolysis generates significant amount hazardous gases (such as CH4 , CO, and H2 ) which are counted as highly environmental pollutants. The utilization of these gases as fuel during pyrolysis could be a suitable choice for protecting the environment. Hence, we pyrolyzed biomass, jute sticks, using a customized pilot furnace, which recycled the generated gases as fuel. We further ball-milled the obtained carbon to make submicron carbon particles. The formation of submicron carbon particles was confirmed with field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, particle size analyzer, and thermogravimetric analysis. The zeta-potential studies confirmed the high negative surface zeta potential of the prepared submicron carbon that was due to its polar functional groups (-OH, COOH, and CO), which were confirmed by Fourier-transform infrared spectroscopy. These polar functional groups facilitate their dispersion in the aqueous solution of biocompatible ethylene glycol and isopropyl alcohol to form water-based environment-friendly inkjet inks. The printing test of the developed ink was performed using a Canon printer (PIXMA; model: G3420) and compared with the performance of commercial inkjet black ink. The results indicate that the performance of the developed inkjet ink is similar to the commercial one.

Gold Nanomaterials and their Composites as Electrochemical Sensing Platforms for Nitrite Detection.

Nitrite is one of the abundant toxic components existing in the environment and is likely to have a great potential to affect human health badly. For that reason, it has become crucial to build a reliable nitrite detection method. In recent years, several nitrite monitoring systems have been proposed. Compared with traditional analytical strategies, the electrochemical approach has a bunch of advantages, including low cost, rapid response, easy operation, simplicity, etc. In this case, noble metal nanomaterials, especially Au-based nanomaterials, have attracted attention in electrode modification because of higher catalytic activity, facile mass transfer, and broad active area for determining nitrite. This review is based on the state-of-the-art, which includes a variety of nanomaterials that have been coupled with gold nanoparticles (AuNPs) for the creation of nanocomposites, and the construction as well as development of electrochemical sensors for nitrite detection over the last few years (2016-2022). A background study on synthesizing different morphological AuNPs and nanocomposites has also been introduced. The fabrication methods and sensing capabilities of modified electrodes are given special consideration.

Enhanced Oxygen Evolution via Electrochemical Water Oxidation using Conducting Polymer and Nanoparticle Composites.

Nano-Co3 O4 was used for electrocatalytic water oxidation due to its promising features of better performance and low cost. An enhanced electrochemical water oxidation performance of the nanoparticles can be achieved by mixing them with other types of highly conductive nano/micro-structured materials. Conductive polymers would be one of the candidates to achieve this goal. Here, we report our recently developed nano-Co3 O4 and polypyrrole composites for enhanced electrochemical water oxidation. We chose polypyrrole as a support of nano-Co3 O4 to obtain highly active sites of nano-Co3 O4 with high conductivity. Morphological and chemical characterization of the prepared materials were performed using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). After immobilizing them individually on fluorine doped tin oxide (FTO) substrate, their electrocatalytic properties toward water oxidation were investigated. The optimum composite materials showed significantly higher electrocatalytic properties compared to that of pure nano-Co3 O4 and polypyrrole. Electrochemical impedance studies indicated that the composite materials possess significantly less electron transfer resistance toward water oxidation reaction compared to that of only polypyrrole or nano-Co3 O4 , while the higher double-layer capacitance and polarization resistance values obtained from fitting of the impedance data represent the faster electrode kinetics in the composite electrocatalyst. Due to the synergetic effect, the optimum nano-Co3 O4 and polypyrrole composites could be represent a novel and promising material for water oxidation.