  There has been budding demand for the fast, reliable, inexpensive,
non-invasive, sensitive, and compact sensors with low power consumption in
various fields, such as defence, chemical sensing, health care, and safe
environment monitoring units. Particularly, an efficient detection of chemical
warfare agents (CWAs) is of great importance for the safety and security of the
humans. Inspired by this, we explored molybdenum carbide MXenes (Mo2CTx; Tx= O,
F, S) as efficient sensors towards selected CWAs, such as arsine (AsH3),
mustard gas (C4H8Cl2S), cyanogen chloride (NCCl), and phosgene (COCl2) both in
aqueous and non-aqueous mediums. Our van der Waals corrected density functional
theory (DFT) calculations reveal that the CWAs bind with Mo2CF2, and Mo2CS2
monolayers under strong chemisorption with binding energies in the range of
-2.33 to -4.05 eV, whereas Mo2CO2 results in comparatively weak bindings of
-0.29 to -0.58 eV. We further report the variations in the electronic
properties, electrostatic potentials and work functions of Mo2CTx upon the
adsorption of CWAs, which authenticate an efficient sensing mechanism.
Statistical thermodynamic analysis is applied to explore the sensing properties
of Mo2CTx at various of temperatures and pressures. We believe that our
findings will pave the way to an innovative class of low-cost reusable sensors
for the sensitive and selective detection of highly toxic CWAs in air as well
as in aqueous media.
