Transition metal oxide/chalcogenide-integrated MXene heterostructures: emerging materials for supercapacitors and water splitting

The growing global demand for sustainable energy solutions necessitates advancements in energy storage and conversion technologies, aligning with the United Nations’ sustainable development goals. MXenes, a novel class of two-dimensional (2D) materials discovered in 2011, have demonstrated immense potential in these fields. Their high surface area, expanded interlayer spacing, metallic conductivity, biocompatibility, abundant redox-active sites, and hydrophilicity make them highly promising for supercapacitors and water-splitting applications. However, MXene layers are prone to agglomeration due to hydrogen bonding and van der Waals interactions, which reduce the active surface area, obscure reaction sites, and hinder ion transport pathways. To overcome these challenges, hybridizing MXenes with transition metal oxides (TMOs) and transition metal chalcogenides (TMCs) can effectively prevent restacking while introducing synergistic functionalities that enhance their overall properties. This review first provides an in-depth discussion on MXene/TMO and MXene/TMC composites for supercapacitors, highlighting their structural advantages and synergistic interactions. It then explores their efficiency in electrocatalytic water splitting, examining their role in enhancing reaction kinetics and overall performance. Finally, the review addresses key challenges, including large-scale synthesis, structural stability, and long-term durability, while offering future research perspectives aimed at optimizing material design, improving performance, and advancing real-world applications in energy storage and conversion.