Highly selective sensing of toxic NO_x gases for environmental monitoring using Ru-doped single walled TiO₂ nanotube: A density functional theory study

Applying density functional theory simulations, in this study, we examine the sensing properties of Ru-TNT surface towards NOx molecules such as NO and NO₂. The obtained results show that Ru doping creates a large-spin density over the Ru-TNT surface, which hints at an increase in the adsorption energy of NOx molecules. The electronic properties of the Ru-TNT surface are significantly altered after NO and NO₂ molecule adsorption, as proven by the larger change in the energy gap values. Moreover, the selectivity study indicates that the Ru-TNT is capable of selectively sensing the NOx molecules in the presence of other gases, e.g., CO₂, CO, NH₃ and H₂O. Using an external positive electric field can resist the strong anchoring of NOx molecules over the Ru-TNT surface, suggesting that material recovery is feasible. Thus, the Ru-TNT structure can be applied as a selective, sensitive, and promising ambient temperature gas sensor for NOx molecules.