Study on the superior gas adsorption and sensing properties of M ₂ Nb ₂ C ₃ (M = Mo, V, and Cr) MXene based sensors in the detection of NO and NO ₂ molecules

Highly sensitive gas sensors for the detection of small molecules of toxic gases (<i>e.g.</i>, NO and NO₂) in air are essential for environmental pollution monitoring and human health protection. In recent years, two-dimensional transition metal carbide MXene materials have attracted much attention due to their excellent electrical conductivity and tunable surface chemistry; however, the theoretical study of polymetallic M₂Nb₂C₃ (M = Mo, V, and Cr) MXene for gas detection is still insufficient. In this article, the adsorption behavior, charge transfer, density of states change, and electron transport response of three bis-transition-metal MXenes (Mo₂Nb₂C₃, V₂Nb₂C₃, and Cr₂Nb₂C₃) on NO and NO₂ molecules are systematically investigated based on the nonequilibrium Green's function approach and density functional theory. The calculation results indicate that all three MXene materials exhibit chemical adsorption of the target gas. Among all of them, the Cr₂Nb₂C₃ material exhibits the most significant change in the <i>I</i>-<i>V</i> curve after NO₂ adsorption, with a sensitivity as high as 70%. Within the voltage range of 0.2-0.7 V, the device maintains significant conductivity enhancement, demonstrating excellent NO₂ detection performance and high sensitivity response capability. This study provides theoretical support and material basis for the construction of high performance and selective multimetallic MXene gas sensors. It opens up a new way for the design of gas-sensitive devices.