Al doped MoS2 for adsorption-based water collection

Abstract

Density functional theory calculations have been performed to investigate Al doping of MoS2 (Al-MoS2), and the adsorption of water molecules on the pristine and doped monolayers. The results show that, H2O@Al-MoS2 has a high degree of dynamical stability allowing for water adsorption even under high-temperature conditions of up to 600 K. This is facilitated by a strong bonding of the dopant with the neighboring Mo, which causes a large charge transfer off the Al atom. Subsequently, Al becomes more electropositive, which gives rise to a bonding interaction with more electronegative oxygen in H2O. The interaction is strong, having the adsorption energy of 1.71 eV. It has an ionic character with the charge transfer between O and Al of 0.16 e-. This makes the electronic band gap of the system adsorption-sensitive changing its size from 0.33 to 1.08 eV for Al-MoS2 and H2O@Al-MoS2, respectively, which could be utilized in a molecular detector. The described effects are exclusive to the doped system. Adsorption energy of H2O at MoS2 is only 0.07 eV, and the molecule has no impact on the electronics of MoS2.