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

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.