Monolayer Ti₂CO₂: A Promising Candidate for NH₃ Sensor or Capturer with High Sensitivity and Selectivity

TLDR

Ti2C is one of the thinnest layers in the MXene family and holds high potential for various applications. The study uses first‑principles simulations to investigate adsorption of NH₃, H₂, CH₄, CO, CO₂, N₂, NO₂, and O₂ on monolayer Ti₂CO₂, aiming to assess its potential as a gas sensor or capturer. Only NH₃ chemisorbs on Ti₂CO₂ with a 0.174‑e charge transfer, producing a dramatic change in its I–V response, and strain further enhances and reversibly controls this adsorption, demonstrating Ti₂CO₂’s high selectivity and sensitivity as an NH₃ sensor or capturer.

Abstract

Ti2C is one of the thinnest layers in MXene family with high potential for applications. In the present study, the adsorption of NH3, H2, CH4, CO, CO2, N2, NO2, and O2 on monolayer Ti2CO2 was investigated by using first-principles simulations to exploit its potential applications as gas sensor or capturer. Among all the gas molecules, only NH3 could be chemisorbed on Ti2CO2 with apparent charge transfer of 0.174 e. We further calculated the current–voltage (I–V) relation using the nonequilibrium Green's function (NEGF) method. The transport feature exhibits distinct responses with a dramatic change of I–V relation before and after NH3 adsorption on Ti2CO2. Thus, we predict that Ti2CO2 could be a promising candidate for the NH3 sensor with high selectivity and sensitivity. On the other hand, the adsorption of NH3 on Ti2CO2 could be further strengthened with the increase of applied strain on Ti2CO2, while the adsorption of other gases on Ti2CO2 is still weak under the same strain, indicating that the capture of NH3 on Ti2CO2 under the strain is highly preferred over other gas molecules. Moreover, the adsorbed NH3 on Ti2CO2 could be escapable by releasing the applied strain, which indicates the capture process is reversible. Our study widens the application of monolayer Ti2CO2 not only as the battery material, but also as the potential gas sensor or capturer of NH3 with high sensitivity and selectivity.