Two-Dimensional th-BCP Monolayer as a Superior Sensor for Detecting Toxic Gases: A First-Principles Study

A two-dimensional tetrahexagonal material BCP monolayer (th-BCP) is designed by applying the Stone–Wales transform to its two-dimensional pentagonal BCP material (penta-BCP). The structural stability and gas adsorption capabilities of the th-BCP are systematically studied using first-principles calculations. The th-BCP monolayer exhibits a direct band gap of 0.806 eV, and its robust structural and thermal stability are verified via phonon spectroscopy and molecular dynamics simulations. The in-plane Young's modulus and Poisson's ratio of th-BCP well indicate that its structure has strong mechanical anisotropy. Then, we investigated the adsorption behavior of eight toxic gas molecules (CO, CO2, NO, NO2, NH3, CH4, SO2, and H2S) on the th-BCP monolayer. Among them, the adsorption energies of NH3 and NO molecules are higher, which are −1.343 and −1.338 eV, respectively. The adsorption energies of NO, CO, H2S, and SO2 molecules are comparatively moderate, ranging from −0.842 to −0.604 eV. Meanwhile, the band gap of the th-BCP with the adsorption of NO and NO2 gas molecules on the surface is obviously changed to 0.396 and 0.151 eV, respectively, resulting in its high sensitivity to these two gas molecules. In addition, the calculation of recovery time for various gas molecules on the surface of the th-BCP reveals its suitability for different gas types across a wide range of temperatures, indicating that the th-BCP should be a gas-sensitive material.