Vimal Kumar Mariappan

This study introduces a novel binder-free 1T MoS ₂ symmetric micro-supercapacitor (1T MoS ₂ SMSC) fabricated on a flexible paper substrate. By fine-tuning the geometry of the electrode fingers and employing a quasi-solid 3M PVA-H ₂ SO ₄ electrolyte, we have achieved high capacitance and excellent cyclic stability across various operational conditions. Electrochemical characterization, including cyclic voltammetry (CV) and chronopotentiometry (CP), revealed that the 1T MoS ₂ SMSC maintains nearly quasi-rectangular CV curves, indicating an ideal capacitive behavior. The device demonstrated a high areal capacitance of 22.5 mF cm ^-2 at 2 mV s ^-1 . In addition, series connections of the devices have shown promising performance metrics suitable for portable electronic applications, achieving significant energy and power density values.

Engineering the intermetallic nanostructures as an effective bifunctional electrocatalyst for hydrogen and oxygen evolution reactions (HER and OER) is of great interest in green hydrogen production. However, a few non‐noble metals act as bifunctional electrocatalysts, exhibiting terrific HER and OER processes reported to date. Herein the intermetallic nickel–antimonide (Ni─Sb) dendritic nanostructure via cost‐effective electro‐co‐deposition method is designed and their bifunctional electrocatalytic property toward HER and OER is unrevealed. The designed Ni─Sb delivers a superior bifunctional activity in 1 m KOH electrolyte, with a shallow overpotential of ≈119 mV at ‐10 mA for HER and ≈200 mV at 50 mA for OER. The mechanism behind the excellent bifunctional property of Ni─Sb is discussed via “interfacial descriptor” with the aid of Kelvin probe force microscopy (KPFM). This study reveals the rate of electrocatalytic reaction depends on the energy required for electron and proton transfer from the catalyst's surface. It is noteworthy that the assembled Ni─Sb‐90 electrolyzer requires only a minuscule cell voltage of ≈1.46 V for water splitting, which is far superior to the art of commercial catalysts.

Direct-current (DC) triboelectric nanogenerators (TENGs) are increasingly recognized as next-generation power sources for widespread applications. Research has recently focused on developing novel materials as active layers for DC TENGs and device configurations to elucidate the working mechanisms. In this work, we report the use of a carbyne (dehydrohalogenated poly(vinylidene fluoride) (PVDF)) film as a positive-type friction layer for DC TENGs for efficient harvesting of rotary energy. The fabricated carbyne-based rotary TENG generates an output voltage (120 V) with excellent mechanical stability and peak power density (500 μW m^-2). The mechanism of DC output generation from the carbyne-based rotary TENG is explained based on halogen removal from PVDF and the electrostatic breakdown effect. Additionally, the humidity effects on the fabricated carbyne-based rotary TENG toward a self-powered humidity sensor are studied in detail with the aid of in situ Raman analysis, Fourier transform infrared spectroscopy, and open-circuit potential measurements. Together, our experimental results demonstrate that using carbyne as an active triboelectric layer for DC TENGs would greatly benefit the next generation of power devices.

Recent research on piezoelectrically driven self-charging supercapacitor power cells (SCSPCs) aims to increase their self-charging performance and understand the charge storage/delivery mechanism. Here, we fabricated a novel SCSPC using a Nafion solid polyelectrolyte separator coated with graphene sheets as supercapacitor electrodes, which exhibited a self-charging process due to the piezo-ionic (PI) effect. The graphene PI-SCSPC can self-charge up to 341 mV under a mechanical stimulus that is superior to many of the reported SCSPCs. The self-charging process is explained based on the creation of the Donnan potential and Nernst's theory of the 2D system. Electrochemical gating coupled with mechanical stimulation was used for understanding the charging dynamics of the graphene PI-SCSPC via examining the critical role of (i) electrochemical doping, and variation in the (ii) voltage of the charge-neutrality point, and (iii) current amplitudes. These findings open a new paradigm for developing novel SCSPCs and understanding their charging dynamics that is of great interest for the realization of next-generation integrated energy cells.

A self-powered water electrolyzer system was constructed via integration of a solar cell with the fabricated CMS/Ni electrolyzer (acts as both anode (OER) and cathode (HER), which demonstrated potential application towards next-generation energy conversion and management systems.

In this study, we report a facile carbothermal method for the preparation of boron-oxy-carbide (BOC) nanostructures and explore their properties towards electrochemical energy storage devices. The formation of lamella-like BOC ceramic nanostructures in which boron suboxides are confined in the carbon matrix was confirmed using high-resolution transmission electron micrographs and X-ray photoelectron spectral analyses. A symmetric supercapacitor (SSC) fabricated using BOC electrodes demonstrated their stable operation over a wide voltage window of 2.0 V in the TEABF₄ electrolyte. The BOC SSC possesses high capacitance (7.26 mF cm⁻²), high energy density (14.53 mJ cm⁻²) with better rate capability, and a long-life cycle. Further, BOC SSC possesses a low equivalent series resistance (1.44 Ω), which in turn leads to the achievement of a high maximal power density (373 mW cm⁻²) that makes it a better alternative to the reported silicon- and carbon-based supercapacitors. In addition, we have also demonstrated a self-charging power system via extrinsically integrating BOC SSC with a thermoelectric power station that further highlights their applications in next-generation energy storage and management sectors.

Two-dimensional ReS₂ nanostructures as an electrode for energy storage devices can be charged using solar cells which can efficiently power electronic devices for a long time, improving its effectiveness for the development of backup energy systems.

Herein, novel paper-like carbine-enriched carbon is prepared and utilized as a bifunctional material for energy harvesting and storage to develop a self-powered system.