M2CS2 (M = Sc, Y) with brand-new MXene phase: The promising candidate as the N/O-containing gases sensor and/or capturer

S-terminated MXenes have been recently successfully synthesized in experiment (Science, 2020, 369, 979). In particular, the atomic arrangement of M2CS2 (M = Sc or Y) is different from all the already known MXenes. Motivated by this, we have theoretically studied the adsorption of 17 kinds of gases (including atmospheric and organic molecules) on M2CS2. Our results revealed that the adsorption of N/O-containing gases on M2CS2 are preferable, and the Y2CS2 exhibits the high chemical activity as compared with Sc2CS2. In detail, the Sc2CS2 could only effectively capture the NH3 and nicotine, while other gases (including NOx, ethanol, acetone and methanol) could also be captured by Y2CS2 because of their strong interaction strengths (Eads < −0.50 eV). In addition, by considering the adsorption energies, charge transfers, density of states and current/voltage relationships of M2CS2-gas systems, we found that Sc2CS2 could be the potential candidate as NH3/NO/nicotine/ethanol gas sensor, and the Y2CS2 exhibits the extremely high sensitivity and selectivity towards NO. Importantly, the M2CS2 is reusable after gas sensing process because of the short recovery times (<0.04 s) at room temperature. Our results will be helpful in understanding the chemical properties and the potential applications of such unique MXene phase (M2CS2).