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.

NO2 gas sensing mechanism of IZO nanorods synthesized by low cost and simple reflux method.

No abstract

The progressive lifestyle and technologically driven economic growth have considerably increased the energy demand across the globe. This has stressed the existing energy resources and adversely affected the environment. To address increased energy demands, it is indispensable to go for a clean carbon-neutral energy source and highly efficient energy storage solutions. Among the different energy storage systems, supercapacitors (SCs) are promising due to their ultrahigh power densities, higher coulombic efficiencies, stable cycling performances, cost-effectiveness, and environment-friendliness. [1][2][3][4] However, their lower energy densities compared to other electrochemical energy technologies like batteries and fuel cells, limit their further applications. Different strategies have been employed for improving the electrochemical properties of SC and an encouraging outlook is to assemble hybrid supercapacitors (HSCs). It consists of two distinct electrodes working via Faradaic, pseudocapacitive, and electric double-layer capacitive (EDLC) charge storage mechanisms. The electrochemistry of two electrode materials in one SC device offers a synergy of high energy storage capacity (Faradaic materials, also known as batterytype materials) and high rate (non-Faradaic materials). However, due to a significant mismatch in the charge dynamics between non-Faradaic and battery-type electrodes, these devices frequently fail to achieve their expected performance. To solve this issue, a double hybridization perspective is envisaged wherein one electrode is EDLC type while the other should be EDLC/battery-type or pseudocapacitor hybrid electrode. [2,5,6] The choice of electrode material thus becomes critical for high-performing energy storage devices. The other factors that are crucial in electrochemical properties are structure, morphology, and composition. Nanostructurization of such electrode materials leads to atomic/molecular level interaction, decreased diffusion pathways, stability in phase changes, etc., and offers improved electrochemical activity. Transition metal selenides have recently attracted much attention over sulfides due to their high electrical conductivity, interesting chemical behavior, and formation of variety of stable selenides such as nickel selenides (NiSe) in terms of stoichiometric and nonstoichiometric compounds. [1] The small difference in electronegativity between Ni (1.9 eV) and Se (2.4 eV), valence electronic configuration of Ni

No abstract