The hurdle of fabricating asymmetric supercapacitor (ASC) devices using a faradic cathode and a double layer anode is challenging due to the required large amount of active mass of anodic material compared to that of the cathodic material during mass balancing due to the large difference in capacitance values of the two electrodes. Here, the problem is addressed by engineering a negative electrode that furnishes an ultrahigh capacitance. An in situ developed metal–organic framework (MOF)‐based thermal treatment is adopted to grow highly porous N‐doped carbon nanotubes (CNTs) containing submerged Co nanoparticles over nano‐fibrillated electrospun hollow carbon nanofibers (HCNFs). The optimized CNT@HCNF‐1.5 furnishes an ultrahigh capacitance approaching 712 F g^–1 with excellent rate capability. The capacitance reported from this work is the highest for any carbonaceous material reported to date. The CNT@HCNF‐1.5 is further used to fabricate symmetric supercapacitors (SSCs), as well as ASC devices. Remarkably, both the SSC and ASC devices furnish incredible performances in all aspects of SCs, such as a high energy density, long cycle life, and high rate capability, displaying decent practical applicability. The energy density of the SSC device reaches as high as 20.13 W h kg^–1, whereas that of ASC approaches 87.5 W h kg^–1.

The development of smart negative electrode materials with high capacitance for the uses in supercapacitors remains challenging. Although several types of electrode materials with high capacitance in energy storage have been reported, carbon-based materials are the most reliable electrodes due to their high conductivity, high power density, and excellent stability. The most common complaint about general carbon materials is that these electrode materials can hardly ever be used as free-standing electrodes. Free-standing carbon-based electrodes are in high demand and are a passionate topic of energy storage research. Electrospun nanofibers are a potential candidate to fill this gap. However, the as-spun carbon nanofibers (ECNFs) have low capacitance and low energy density on their own. To overcome the limitations of pure CNFs, increasing surface area, heteroatom doping and metal doping have been chosen. In this review, we introduce the negative electrode materials that have been developed so far. Moreover, this review focuses on the advances of electrospun nanofiber-based negative electrode materials and their limitations. We put forth a future perspective on how these limitations can be overcome to meet the demands of next-generation smart devices.

Green synthesis of silver nanoparticles (AgNPs) using plant extracts has ascended as a hopeful practice due to its low cost, easy, fast, and environmentally benign method. The present study established an eco-friendly method to synthesize AgNPs by reacting silver nitrate with Ziziphus mauritiana root bark extract at room temperature and in neutral conditions. The formation of AgNPs was detected by the change from light yellow to dark brown color of the reaction mixture. The appearance of peaks at 422-432 nm in the UV-visible spectroscopy further ascertained the formation of AgNPs in the solution. Functional groups in the plant extract which have potential roles in the reduction, capping, and stabilization of AgNPs were detected by FTIR spectra. The surface morphology and presence of silver, carbon, and oxygen in the AgNPs were detected by FESEM and EDX analysis. The spherical shape and average size (16.73 ± 4.94 nm) of the particles were determined from the TEM images and the fcc crystalline nature was established by XRD analysis. The synthesized AgNPs exhibited higher DPPH radical scavenging capacity (IC50 = 17.55 ± 0.495 µg/mL) than the extract (IC50 = 37.02 ± 1.00 µg/mL). The silver nanoparticles showed greater antimicrobial activity against Gram-positive Staphylococcus aureus (ATCC 25923), Gram-negative Escherichia coli (ATCC 25922), Salmonella typhi (ATCC 14028), and Shigella sonnei (ATCC 25931) on the agar well diffusion method. The results of the study highlight the potential application of the Z. mauritiana extract-mediated AgNPs for the development of eco-friendly, cheap, and cost-effective biomedical products.

For sustainable hydrogen production through water splitting, the rational engineering of economical and effective electrocatalysts/nanomaterials for the hydrogen evolution reaction (HER) is essential. In this work, we describe the logical design and in-situ development of a nickel-doped cerium metal-organic framework (Ni/Ce-BTC@NF) directly on 3D nickel foam (NF), designing a binder-free (freestanding) electrode with a distinctive three-dimensional (3D) nanopillar-like structure. The unique design of a crystalline Ce-BTC framework with evenly dispersed nickel while maintaining the intrinsic rod-like shape upon doping is confirmed by structural and morphological investigations. Electrochemical measurements reveal that Ni doping significantly enhances HER activity in alkaline medium, with Ni/Ce-BTC@NF achieving overpotentials of 108.9 mV and 196.1 mV to sustain 10 mA cm⁻² and 50 mA cm-2, respectively, outperforming pristine Ce-BTC@NF. Excellent durability is demonstrated by the material’s steady activity throughout a 24-hour time of continuous operation. The Ni/Ce-BTC@NF (−) // RuO2@NF (+) electrolysis configuration exhibits competitive total water-splitting performance requiring 1.67 V (cell voltage) at 10 mA cm-2. This research offers a viable method for designing cerium MOFs-based electrocatalysts with hierarchical topologies and modulated electronic structures for effective hydrogen generation.