Adsorption and gas-sensing properties of formaldehyde on defective MoS[formula omitted] monolayers: A first-principles study.

Formaldehyde (CH 2 O) is an indoor hazardous gas and a respiratory marker for lung cancer patients, thus its adsorption and detection are of particular significance. 2H-MoS 2 has a wide range of applications in gas sensors. However, its pristine form is chemically inert and not suitable for the adsorption and detection of CH 2 O. Here, we systematically investigated the adsorption and gas-sensing properties of defective 2H-MoS 2 to CH 2 O based on first-principles calculations. The S vacancy, substitutional doping and adsorption of transition-metal (TM) atoms in the MoS 2 monolayer are considered. We find that the S vacancy effectively enhances the adsorption of CH 2 O and results in significant charge transfer. The substitutional doping of TM atoms on both S and Mo sites is hard to form in equilibrium conditions for the high formation energy. The adsorption of TM atoms on MoS 2 can easily occur for the rather low adsorption energy. Cr and Mn energetically prefer to be adsorbed above the S site, while V, Fe, Co, Ni and Cu energetically prefer to be adsorbed above the Mo site. The TM-adsorbed MoS 2 can then strongly adsorb CH 2 O molecules and results in significant charge transfer, acting as a gas-sensing candidate material for the detection and adsorption of CH 2 O. The adsorption configurations, density of states, adsorption energy, charge transfer and charge density differences are calculated and discussed. These results are of significance to adsorb the toxic CH 2 O gas and design its gas sensors using MoS 2. [ABSTRACT FROM AUTHOR]