Adsorption and sensing mechanism of B-doped MoSi2N4 monolayer towards hazardous gases: A DFT investigation

Abstract

Designing effective gas sensors is an urgent task in detecting and removing trace amounts of hazardous gas molecules (HGMs) released from industrial production. In this study, the first-principles calculations were conducted to investigate the adsorption behaviors of eight HGMs (CO, NH3, NO, NO2, SO2, H2S, CH4, H2CO) on the pristine and B-doped MoSi2N4 (B-MSN) monolayers. And their corresponding adsorption parameters, bonding characteristics, electron properties and work function were systematically explored to reveal the micro-sensing mechanism of B-MSN monolayer towards HGMs. The results indicate that all HGMs are physically adsorbed onto the pristine MoSi2N4 monolayer due to the small adsorption energies of −0.16 eV∼ −0.36 eV and minimal charge transfer of 0.019 e ∼ 0.043 e. However, the introduction of B atoms immediately triggers a transition from physisorption to chemisorption for all HGMs, with adsorption energies ranging from −1.13 to −3.45 eV. The strong capture ability of B-MSN monolayer is primarily contributed by the strong hybridizations between B−2p and 2p orbitals of gas molecules in the energy range of −12.5 eV∼ −5.0 eV. Additionally, the noticeable changes in conductivity and work function demonstrate the high sensitivity of the B-MSN monolayer to HGMs. Furthermore, the recovery time of CH4 at 300 K, 400 K and 500 K is respectively estimated to be 949.06 s, 0.02 s and 2.43 × 10−5 s, thus the B-MSN monolayer is regarded as a promising and reusable gas sensor for the detection of CH4. Our studied results can provide a theoretical basis for the design and fabrication of MoSi2N4-based gas sensors.