Adsorption of gas molecules on intrinsic and defective MoSi2N4 monolayer: Gas sensing and functionalization

The adsorption behaviors of CO, NH3, NO, and NO2 on intrinsic and defective MoSi2N4 monolayer, and the electronic properties, magnetic and gas sensing properties are researched by first-principles calculations. The low adsorption energies of gas molecules adsorbed on the intrinsic MoSi2N4 systems demonstrate that physisorption characteristics. The CO and NH3 adsorbed on MoSi2N4 systems exhibit non-magnetic semiconductor behavior, whereas the NO and NO2 adsorbed on MoSi2N4 systems emerge magnetic semiconductor behavior. The recovery time of the CO, NH3, NO, and NO2 adsorbed on MoSi2N4 systems is 1.70 x 10-11, 3.6 x 10-10, 2.60 x 10-11, and 3.21 x 10-10 s, respectively. Meanwhile, the sensitivities are 0.42 (CO), 0.41 (NH3), 0.51 (NO), and 0.27 (NO2) for the intrinsic MoSi2N4, respectively, demonstrating that MoSi2N4 can be an invertible sensor to detect CO, NH3, NO, and NO2 in the environment. Interestingly, the N defect MoSi2N4(VN/MoSi2N4) system displays magnetic semiconductor features, while the NO adsorbed VN/MoSi2N4 system has non-magnetic semiconductor feature. The Si defect MoSi2N4 (VSi/MoSi2N4) system appears magnetic semimetal characteristics, while the NH3 adsorbed VSi/MoSi2N4 system appears nonmagnetic semiconductor characteristics. Compared with the intrinsic MoSi2N4, the defect MoSi2N4 adsorption systems has stronger adsorption energy, suggesting that the stronger capture ability of the defect MoSi2N4 for CO, NH3, NO, and NO2.