Two-dimensional MXenes as emerging thermoelectric materials: From fundamentals to composite design strategies and applications

MXenes are an outstanding category of two-dimensional transition-metal nitrides, carbides and carbonitrides that have surfaced as interesting candidates for thermoelectric study due to their superior electrical conductivity, adjustable surface chemistry and layered structure. This review thoroughly analyzes the thermoelectric characteristics of MXene-based materials, starting with an overview of MXene chemistry and production and then providing an in-depth explanation of the fundamental mechanisms related to electrical and heat transport in these materials. To provide a consistent design framework, a methodical examination of techniques to improve thermoelectric performance such as interlayer spacing control, surface termination engineering, doping and energy filtering, intercalation, and defect/interface engineering is carried out in this article. The thermoelectric characteristics of composition-specific pristine and doped MXenes are then examined in the article, which also identifies important gaps in experimental data for additional MXene families and emphasizes the relative advantages of Mo-based devices. By combining polymers, inorganic phases and carbon-based materials, MXene-based composite thermoelectrics are investigated as a potential means of reducing intrinsic limitations through interfacial and hierarchical transport phenomena. The review describes the principal problems of stability, measurement repeatability, scalability and device integration while offering a balanced viewpoint on prospective research trajectories. This study characterizes MXenes not as independent high-efficiency thermoelectrics, but as adaptable and modifiable components for advanced thermoelectric systems.