Two-dimensional transition metal MXene-based gas sensors: A review

As an emerging star in the family of two-dimensional (2D) materials, 2D transition metal carbides, carbonitrides and nitrides, collectively referred to as MXenes, have large specific surface area, rich active sites, metallic conductivity and adjustable surface chemical properties. These features make MXenes promising candidates for gas-sensing materials. For the past few years, MXene-based sensors have drawn increasing attention due to their enhanced sensor performance. Based on this, this review systematically represents the structure, synthesis methods and properties of MXenes, and summarizes their applications in gas sensors. Firstly, the types, structure, main synthesis methods and properties of MXenes are introduced in a comprehensive way. Next, the corresponding design principle and working mechanism of MXene-based gas sensor are clarified. Subsequently, the sensing performances of pristine MXenes and the MXene-based nanocomposite are discussed. Finally, some future opportunities and challenges of MXene-based sensors are pointed out.