Babasaheb. N. Dole

Two-dimensional (2D) materials have emerged as promising electrode materials for high-performance supercapacitors due to their unique structural, electrical, and surface properties. Materials such as graphene, MXenes, molybdenum disulfide, and transition metal dichalcogenides exhibit large specific surface area, excellent electrical conductivity, tunable surface chemistry, and abundant active sites for charge storage. These characteristics significantly enhance electrochemical performance, including high capacitance, improved energy density, rapid charge–discharge capability, and long cycling stability. This chapter discusses the synthesis strategies, structural engineering, and electrochemical mechanisms of 2D materials used in supercapacitor electrodes. It also highlights the role of hybrid and composite architectures, such as metal oxide–2D material composites and conductive polymer hybrids, in improving electrochemical performance. Furthermore, recent advancements in flexible and wearable supercapacitor devices based on 2D materials are explored. The chapter concludes with current challenges and future perspectives for developing next-generation energy storage devices using advanced 2D nanomaterials.

In the present work, 5% Ni‐doped ZnO/TiO ₂ nanocomposites were synthesized via a coprecipitation method to investigate their potential for sunlight‐assisted photocatalytic degradation of RhB dye. X‐ray diffraction analysis confirmed a hexagonal crystal structure with an increase in crystallite size upon the incorporation of TiO ₂ and Ni into the ZnO lattice. Morphological studies revealed uniformly distributed, well‐separated, and nearly spherical particles with an average size of 36.4 nm. Raman spectroscopy indicated enhanced structural defects and the presence of local surface distortions in the Ni‐doped samples. The 5% Ni‐doped ZnO/TiO ₂ nanocomposites exhibited a remarkable photodegradation efficiency of 93.3% for RhB dye under 120 min of natural sunlight irradiation, outperforming both pure ZnO and TiO ₂ ‐based ZnO counterparts. Scavenger analysis confirmed that hydroxyl radicals (•OH) are the major reactive species responsible for the photocatalytic degradation process. The enhanced photocatalytic activity can be attributed to the synergistic effects of Ni doping, increased crystallite size, and defect‐induced active sites, making the material a promising candidate for environmental remediation applications.

This study focuses on the synthesis, structural, morphological characterization, and functional analysis of a tungsten carbide (WC) based p–n heterojunction nanocomposite comprising Co ₃ O ₄ /TiO ₂ (WPCT) and 5% Ni‐doped Co ₃ O ₄ /TiO ₂ (WNCT), engineered for multifunctional applications. XRD analysis confirmed the coexistence of Co ₃ O ₄ (cubic spinel), TiO ₂ (anatase), and WC phases with crystallite sizes around 38.60 nm. Raman and FT‐IR spectra further validated the structural integrity of the composite, while FESEM revealed that Ni doping promotes nanorod morphology, thereby increasing surface‐to‐volume ratio. BET analysis demonstrated a significant increase in surface area from 45.63 m ² /g (WPCT) to 93.99 m ² /g (WNCT). UV–vis absorption confirmed band gap narrowing from 2.46 to 1.98 eV due to Ni doping and it improving visible‐light harvesting. Photoluminescence studies indicated reduced electron–hole recombination, consistent with improved charge separation across the p–n heterojunction. Functionally, WNCT exhibited superior degradation efficiency with 99.6% mixed dye degradation within 40 min and enhanced photosensitivity (21.78%) as well as excellent gas sensing performance toward n‐butanol with a response of 81% at room temperature. These results demonstrate that the synergistic effects of WC conductivity, Ni doping and nanorod morphology contribute to both outstanding photocatalytic efficiency and sensitive gas detection, establishing WNCT as a promising multifunctional material for environmental remediation and sensing applications.