Recent advances in MXene gas sensors: synthesis, composites, and mechanisms

Abstract MXenes, a class of two-dimensional (2D) transition metal carbides and nitrides, have emerged as promising materials for high-performance gas sensors due to their unique combination of high electrical conductivity, tunable surface chemistry, and large specific surface area. This review highlights recent advances in MXene-based gas sensing materials, covering their synthesis strategies, structure–property relationships, and applications in both pristine and composite forms. We discuss conventional hydrofluoric acid etching and recent fluorine-free methods for MXene synthesis, and examine how these approaches affect surface terminations, interlayer spacing, and defect profiles relevant to gas sensing. The gas-sensing performance of pristine MXenes and their composites with metal oxides, transition metal dichalcogenides (TMDs), rGO, and conductive polymers is systematically analyzed, along with the underlying sensing mechanisms. Finally, current challenges and future perspectives for MXene-based gas sensors are addressed, with emphasis on enhancing sensitivity, selectivity, and ambient stability for next-generation sensing platforms.