Monolayer Penta-BeAs₂: A Promising 2D Materials for Toxic Gas Sensor with High Selectivity

The discovery of novel materials with high gas sensing selectivity is a key driver of gas sensor technology. Based on the recently reported two-dimensional (2D) pentagonal BeP₂, we introduce penta-BeAs₂ as a new member of the pentagonal family of materials for toxic gas sensors based on density functional theory (DFT). For electronic applications, a band structure calculation showed that penta-BeAs₂ has indirect band gaps of 0.38 and 0.79 eV, using GGA–PBE or HSE functionals. Stability analysis confirmed that penta-BeAs₂ is dynamically, mechanically, and thermally stable. The adsorption of toxic gases (CO, NO, and NO₂) and nontoxic gases (H₂, N₂, H₂O, and CO₂) on the penta-BeAs₂ monolayer was studied. The contrasting adsorption behavior observed between toxic and nontoxic gases on penta-BeAs₂ (physisorption vs chemisorption) underscores its high selectivity for toxic gas-sensing applications. Adsorption energies for toxic gases fall within a moderate range (0.4–0.8 eV), indicating good reversibility and short recovery times at room temperature. Additionally, the quantum transport properties of penta-BeAs₂ were studied using the nonequilibrium Green’s function (NEGF) approach, confirming strong sensitivity and selectivity toward toxic gases.