Multifunctional MXenes for next-generation energy devices: From photodetectors to solar cells and supercapacitors

Two-dimensional (2D) MXenes transition-metal carbides, nitrides and carbonitrides have emerged as a versatile class of materials with exceptional electrical conductivity, tunable work function, rich surface chemistry and structural adaptability. While their application in individual energy technologies such as photodetectors (PDs), solar cells, or supercapacitors has been extensively explored, a unified understanding of their multifunctional capabilities across these domains remains lacking. This review provides a mechanism-driven, cross-application analysis of MXenes, elucidating the shared physicochemical attributes that underpin their performance in optoelectronic and electrochemical energy devices. The synthesis structure–property relationships are systematically discussed, with emphasis on termination engineering, interlayer spacing control and heterostructure design as universal performance-enhancement strategies. Comparative evaluations reveal that MXene integration can simultaneously boost responsivity in PDs, power conversion efficiency in solar cells, and capacitance in supercapacitors through synergistic improvements in charge transport, light absorption and ion accessibility. Importantly, this work introduces the concept of universal MXene architectures, single-material platforms engineered to function across multiple device types, opening new pathways toward integrated energy harvesting, storage and sensing systems. We further outline key challenges, including stability under ambient conditions, scalable fabrication, multifunctionality optimization and propose future research directions leveraging green synthesis, computationally guided design and emerging MXene quantum dot technologies. By bridging currently isolated research efforts, this review establishes MXenes as a pivotal enabler for next-generation, high-efficiency and sustainable multifunctional energy devices.