Photocatalytic activity of MoS2 with water monolayers: Global optimization

Abstract

Atomically thin MoS2 has emerged to be promising for photocatalytic water splitting benefiting from its suitable geometrical and electronic structure for light harvesting. A better understanding of how water molecules affect the band edge levels of MoS2 is critical for promoting the interfacial reactivity. Here we determine the structures of water monolayers on MoS2 using global optimizations achieved by molecular dynamics in combination with local minimization. It is shown that cyclic water clusters are formed on surface through hydrogen-bonding network. The absolute band edge positions are explored taking into account the derivative discontinuity of the exchange-correlation functional. Shifts in band edges are observed with the increase in H2O coverage while band gaps tend to be slightly decreased. In particular, the band alignment relative to water redox potentials has been investigated in detail. We find that the dimer configuration is likely to suppress the hydrogen evolution reaction (HER), while the polygon clusters lift the conduction band by 0.2-0.7 eV and thus they would enhance HER. This effect is explained in terms of the linear dependence of band edge offset on interface electric dipole arising from water assemblies.

Many-Body Calculations of Excitons in Two-Dimensional GaN

“…The resulting GLLBSC gaps are comparable to the G 0 W 0 gaps in both cases, while the computational effort remains at an LDA or GGA level. This method has been adopted to predict the band edges of MoS 2 with the adsorption of water molecules, which are useful for studying its photocatalytic performance [72]. Second, we can see that when going from the bulk crystal to the monolayer, the QP band gap is increased by 1.24 eV according to G 0 W 0 calculations.…”