Fabrication strategies and electrochemical performance of emerging 2D MXene-based hybrid nanomaterial electrodes for high-performance supercapacitors: A review

MXenes are a rapidly emerging family of two-dimensional (2D) transition-metal nitrides, carbides, and carbonitrides that have attracted significant attention since the first report of Ti 3 C 2 T x synthesis by Gogotsi and co-researchers at Drexel University in 2011. Owing to their intrinsically layered structure, atomic-scale thickness, metallic conductivity, excellent hydrophilicity, tuneable surface chemistry, and mechanical flexibility, MXenes have demonstrated exceptional potential in diverse applications, mostly electrochemical energy storage. Their exceptionally large specific surface area, superior electrical conductivity, and abundant surface functional groups make MXenes highly suitable for both electric double-layer and pseudocapacitive charge-storage mechanisms. This review critically surveys current developments in 2D MXene-based supercapacitors, with a prominence on synthesis routes, structural characteristics, and the influence of fabrication strategies on electrochemical performance. Key aspects such as charge-storage mechanisms, electrode architecture design, and the development of hierarchical and hybrid composites for enhancing capacitance, energy density, and operating voltage are discussed in detail. In addition, the role of electrolyte selection, micro-supercapacitor fabrication methods, and the impact of MXene sheet size and morphology on device performance are briefly addressed. By consolidating state-of-the-art developments, this review highlights potential of MXene-based composites to meet industrial requirements for durable, flexible, and high-efficiency energy storage devices. Finally, existing challenges such as long-term stability, oxidation resistance, and scalable processing and future directions for translating MXene supercapacitors bridging laboratory-scale research and real-world applications are outlined. Overall, this review aims to deliver guidance for the rational engineering of next-generation MXene hybrid high-performance electrodes for supercapacitor applications.