Extrinsic Pseudocapacitive NiSe/rGO/g-C3N4 Nanocomposite for High-Performance Hybrid Supercapacitors.

Battery-type materials with ultrahigh energy density show great potential for hybrid supercapacitors (HSCs). In this work, we have developed a nickel selenide (NiSe)/reduced graphene oxide (rGO)/graphitic carbon nitride (g-C3N4) ternary composite as a promising positive electrode for hybrid supercapacitors (HSCs). The extended π-conjugated planar layers of g-C3N4 promote strong interconnectivity with rGO, which further enhances surface area, surface free energy, and efficient electron/ionic path. Additionally, it establishes clear ion diffusion pathways, serving as ion reservoirs during charge and discharge and facilitating efficient redox reactions. As a result, the NiSe/g-C3N4/rGO nanocomposite electrode displayed a specific capacity of 412.6 mA h g-1 at 1 A g-1. Later, the HSC device was assembled using the nanocomposite as the positive electrode and activated carbon as the negative electrode, which delivered an energy density of 65.2 Wh kg-1 at a power density of 750 W kg-1. Notably, the HSC device maintained excellent cyclic stability, preserving 93.3% of its initial performance and Coulombic efficiency of 86.6% for 10,000 charge-discharge cycles at 5 A g-1. These findings underscore the potential utility of NiSe/g-C3N4/rGO as a versatile and effective electrode material for the strategic development of HSC devices.

Emergence of Ni-Based Chalcogenides (S and Se) for Clean Energy Conversion and Storage.

Nickel chalcogenide (S and Se) based nanostructures intrigued scientists for some time as materials for energy conversion and storage systems. Interest in these materials is due to their good electrochemical stability, eco-friendly nature, and low cost. The present review compiles recent progress in the area of nickel-(S and Se)-based materials by providing a comprehensive summary of their structural and chemical features and performance. Improving properties of the materials, such as electrical conductivity and surface characteristics (surface area and morphology), through strategies like nano-structuring and hybridization, are systematically discussed. The interaction of the materials with electrolytes, other electro-active materials, and inactive components are analyzed to understand their effects on the performance of energy conversion and storage devices. Finally, outstanding challenges and possible solutions are briefly presented with some perspectives toward the future development of these materials for energy-oriented devices with high performance.