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Supercapacitors, in particular, are gaining popularity in electronic devices, electric vehicles, and emergency power supplies due to their safe operation, rapid charge/discharge rates, high power density, and extended lifespan compared with batteries and fuel cells. However, to further enhance the energy density, widening the operating voltage window through the design of asymmetric supercapacitors and increasing the capacitance of electrode materials have been explored. This study focuses on the development of a sea-urchin-like morphology composed of bimetallic copper–cobalt carbonate hydroxides (CCCOHs) by using a hydrothermal method to optimize the surface morphology and improve energy storage capabilities. The synthesized CCCOH-24 sample demonstrated an impressive specific capacitance of 675 C g–1 at a current density of 15 A g–1 and maintained 87% stability at 30 A g–1. When assembled into an asymmetric solid-state supercapacitor with activated carbon, the device achieved an energy density of 63 Wh kg–1 and a power density of 10.2 kW kg–1, retaining over 88% capacitance after 10000 cycles. This study highlights the potential of CCCOHs with tailored morphologies for advanced supercapacitor applications, offering a pathway to enhance the energy storage performance and stability. [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, new type of convolution and correlation theorems associated with quadratic phase Fourier transform (QPFT) are studied. Applications of that in multiplicative filter design, which may be useful in optics and signal processing to recover the signals, are also discussed. Besides that, the real Paley–Wiener (PW) and Boas theorem for QPFT are proved, which analyses the characteristics of the signals associated with QPFT in the L2$$ {L}^2 $$ domain. [ABSTRACT FROM AUTHOR]

In this paper, we explore various uncertainty principles within the framework of the quaternion quadratic phase Fourier transform (QQPFT), which is the quaternion extension of the quadratic phase Fourier transform (QPFT). First, using the orthogonal plane split (OPS) method of quaternions, we observe the relation between QPFT and QQPFT. Later, using the OPS method, we formulate sharp Young–Hausdorff inequality, Pitt’s inequality, logarithmic uncertainty principle, entropy uncertainty principle, Heisenberg uncertainty principle, and Nazarov’s uncertainty principle for QQPFT. [ABSTRACT FROM AUTHOR]

Ternary metal sulfides (TMSs) have garnered significant attention as alternative electrode materials for rechargeable metal‐ion battery anodes and electrodes for electrochemical supercapacitors (SCs). With the escalating costs of lithium, research has shifted toward alternative sources like sodium‐ion batteries (NIBs) and potassium‐ion batteries (KIBs), offering cost‐effectiveness and greater natural abundance globally. However, pursuing suitable electrode materials beyond lithium‐ion batteries (LIBs), such as NIBs, KIBs, and SCs with enhanced energy and power density, remains a formidable challenge. In this context, TMSs demonstrate remarkable reversibility as NIB, KIB, and SC electrode materials, showcasing multi‐electron redox reactions, improved electronic conductivity, and higher theoretical capacities. Numerous research articles have highlighted the promising future of TMSs as electrodes for electrochemical energy conversion and storage (EECS). Nonetheless, practical applications are hindered by limitations, including structural stability during long‐standing cyclability, electronic conductivity, and scalability. This review systematically demonstrates how varying synthesis routes can tailor nanostructures and their influence on electrochemical activity. Additionally, an in‐depth literature survey is provided on the electrochemical performances of TMSs in NIBs, KIBs, and SCs and summarize recent advancements with the best available literature. Moreover, promising prospects and challenges are highlighted, expressing optimism that TMSs will emerge as pivotal electrodes for EECS. [ABSTRACT FROM AUTHOR]

A highly functioning copper cobalt-based ternary phosphide (CCP) cathode was engineered from a copper cobalt carbonate hydroxide (CCH) material via a gas–solid thermal route, resulting in a 3D spatial morphology with a hierarchical architecture and porosity. Preliminary electrochemical testing revealed the superiority of the CCP cathode with a specific capacity value of 2392 C g–1 at 10 A g–1 and a capacity retention of 94.4% over 5000 cycles at 40 A g–1. The morphological advantages of CCP with its 3D hierarchical architecture, highly porous network, and numerous nanospikes with sharp edges and surface defects offer tremendous active sites and ion transport channels for better charge storage performance. The CCP//activated carbon electrode (ACE) hybrid supercapacitor (HSC) device delivered a capacity value of 284.5 C g–1 at 10 A g–1 and a 92.3% retention in capacity for 10 000 cycles at a high current density of 30 A g–1. Furthermore, the fabricated device provided high energy and power density values of 129.15 Wh kg–1 and 66.4 kW kg–1, respectively, and powered a red LED for 1 min. Thus, this work efficiently provides knowledge on the development of a Cu3P–CoP electrode material from optimizing morphological features and synthetic routes, which leads to achieving superior functioning cathode materials for hybrid supercapacitors in the current energy storage era. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides (TMDs) are fascinating and prodigious considerations in the electrochemical energy storage sector because of their two dimensional chemistry as well as heterogeneous characteristics. Herein, we synthesized interconnected WS2 nanosheets by a hydrothermal method followed by sulphuration at 850 °C in an argon atmosphere. The ultrathin WS2 nanosheet array is endowed with an excellent specific capacitance of 74 F g−1 at the current density of 3 A g−1 up 7000 cycles. Moreover, a symmetric supercapacitor was fabricated using WS2 nanosheets, which provided the admirable high specific capacity of 6.3 F g−1 at 0.05 A g−1 with the energy and power density of 5.6 × 102 mW h kg−1 and 3.6 × 10 5 mW kg−1, respectively. Density functional theory (DFT) simulations revealed the presence of populated energy states near the Fermi level resulting in a high quantum capacitance value, which supports the experimentally achieved high capacitance value. The attained results recommend interconnected WS2 nanosheets as a novel, robust, and low-cost electrode material for supercapacitor energy storage devices. [ABSTRACT FROM AUTHOR]

Composite of dextrose-derived oxygen-rich carbon spheres and graphene oxide, synthesised using a cost-effective and easy hydrothermal process, was used as an active material in two of the trending and promising energy storage devices. The surface morphology and properties of the composite were studied using scanning electron microscope, X-ray diffractometer, energy dispersive X-ray analysis, elemental mapping and Raman spectra. To analyse the electrochemical behaviour of the material, several electrochemical techniques such as cyclic voltammetry (CV), chronopotentiometry, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation study were used. The reversibility of Fe2+/Fe3+ redox species and resistance offered by electrolyte towards the modified electrode were studied using CV, EIS and Tafel studies. Further evaluation of efficacy of the active material towards the iron redox flow battery (IRFB) of 132 cm2 area was analysed by performing charge discharge studies at varied current densities. Substantial increase in the electrochemical performance of the IRFB with a coulombic efficiency (CE) 93% along with the good life cycle stability up to 25 cycles was observed. The composite was also used as a superior electrode material for supercapacitor application resulting in significant enhancement in the electrochemical performance with specific capacitance of 610 F g−1 and CE of 83% with 93% retention up to 1600 cycles. [ABSTRACT FROM AUTHOR]

The multiple oxidation states of redox‐active materials enable them to store high‐energy better than the commonly used carbon‐based electrode materials. Accounting for these advantages, designing asymmetric supercapacitors by coupling redox‐active materials as positive electrodes with carbon‐based negative electrodes becomes a very attractive strategy. Herein, reduced graphene oxide‐wrapped hexagonal WO3 nanorod (rGO‐WO3 NR) by simple hydrothermal synthesis method is synthesized. Because of improved reaction kinetics resulting from the close contact between rGO and WO3 NRs, rGO‐WO3 NR demonstrates superior electrochemical properties than pure WO3. Motivated by the very high areal capacitance (2.5 F cm−3 at the applied current of 30 mA cm−2), an asymmetric SC device by combining rGO‐WO3 NR with activated carbon is assembled. The as‐assembled rGO‐WO3 NR//activated carbon asymmetric supercapacitor device demonstrates outstanding electrochemical performance in an operating voltage window of 1.2 V, admirable cycling stability of ≈95% (even after 14 000 cycles), with an energy density of 24.1 Wh Kg−1 at a power density of 1532.6 W Kg−1. These demonstrate the combination of redox‐active materials with high energy density can importantly boost the energy storage capacity of a supercapacitor. [ABSTRACT FROM AUTHOR]