Enhanced NH3 and NO sensing performance of Ti3C2O2 MXene by biaxial strain: insights from first-principles calculations

In this study, we investigate the adsorption properties of CO, NH3, and NO gases on Ti3C2O2 MXene surfaces through density functional theory (DFT) calculations. A comprehensive analysis of the adsorption preferences, electronic properties, work function (phi), sensitivity (S), and recovery time (tau) was conducted, focusing on the effects of biaxial strain (epsilon) ranging from -2% to 4%. At free strain, toxic gases can adsorb onto the Ti3C2O2 surface, with adsorption energies (Ead) of -0.096 eV (CO), -0.344 eV (NH3), and -0.349 eV (NO), indicating moderate interactions between NH3, NO and the Ti3C2O2 surface, while CO displays weaker physisorption. Electron density difference (EDD) and electron localization function (ELF) analyses underscore the electron transfer mechanisms, supporting the enhanced sensitivity of Ti3C2O2 for NH3 and NO detection. The influence of epsilon on gas adsorption behaviour was also studied, demonstrating that tensile strain enhances NH3 adsorption (Ead = -0.551 eV at epsilon = 4%), while NO exhibits an inverse trend under compressive strain (Ead = -0.403 eV at epsilon = -2%). The S based on a change rate of phi was evaluated to be around 12% and 6% for NH3 and NO, respectively, within the calculated strain range, indicating sufficient detection capability. Additionally, the tau for NH3 and NO detection was computed. At 0% strain and 300 K, the tau values for NH3 and NO are in the microsecond range, suggesting that detecting these gases under normal conditions poses a challenge. However, strain-tuned Ti3C2O2 and lowered temperature enhance the gas sensing performance, with increased tau values at tensile strain for NH3 and compressive strain for NO. These results suggest that Ti3C2O2 MXene, when tuned with biaxial strain, is a promising candidate for detecting NH3 and NO at low to room temperatures.