Advances in two dimensional materials for supercapacitor applications: From metal carbides to metal borides and beyond

The advent of two-dimensional (2D) materials has transformed the energy storage domain, especially in the advancement of high-performance supercapacitors. This review examines the recent advancements in 2D materials for supercapacitor applications, with a focus on transition metal dichalcogenides (TMDs), MXenes, layered double hydroxides (LDHs), metal borides (MBenes), and porous frameworks such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). These materials exhibit elevated surface area, tunable electronic structure and surface chemistries, enabling tailored functionalization for advanced energy storage devices. A comprehensive analysis is presented on the synthesis strategies, structural design, and performance optimization techniques of these materials, emphasizing their synergistic interactions within composite systems. Advanced operando characterization techniques, including in situ spectroscopy, electron microscopy, and electrochemical measurements, are discussed, which provide real-time insights into charge storage mechanisms, ion diffusion kinetics, and material stability under operational conditions. These techniques bridge the gap between fundamental understanding and practical applications, offering pathways to enhance the design and efficiency of supercapacitors based on 2D materials. The review concludes current challenges and future directions in this field, emphasizing the importance of addressing scalability and cost-effectiveness. The insights presented here provide a useful reference for leveraging 2D materials for sustainable and high-performance supercapacitors.