Improving Hydrogen Evolution by Mn Doping MoS2 Nanosheets: DFT QTAIM analysis

In a recent combined experimental and theoretical paper, periodic DFT calculations and Bader’s QTAIM analysis explain, at the atomistic level, the enhancement of the performance of MoS₂ 2D material for the hydrogen evolution reaction (HER), when it is doped with Mn. Periodic DFT-QTAIM calculations performed with BAND indicate that the incorporation of Mn atoms into the basal plane of MoS₂ nanosheets activates all in-plane S atom sites and three Mo atoms neighboring the Mn dopant, thereby reducing the adsorption free energy of H atoms, improving thus the HER catalytic activity of the surface (see article’s Figure 6). The DFT-QTAIM calculations agree well with the experimental data for enhanced HER performance of Mn-MoS₂.

In order to explore the effects of the doping locally (close to the doping atom) and globally, the
adsorption of 32 H atoms to cover the whole super-cell was considered. One H atom was
considered atop each symmetrically equivalent S atom (16 in total) and another 16 H atoms in an
atop Mo position (see article’s Figure 7). According to QTAIM, for the pristine MoS₂ monolayer,
each of the H atop S atom is absorbed via a covalent S-H bond, while the other 16 H atoms are not
bonded directly to the material surface. This explains why the basal plane of pristine MoS₂ is
inert for HER. As for doped Mn-MoS₂ monolayer, the 16 H atop S atoms remain covalently
bonded. However, in sharp contrast, the 16 H atop Mo atoms (in-hollow H atoms) are absorbed by
S atoms via weak bonds. Further, some of these in-hollow H atoms also form a weak bond with Mo
neighboring the Mn dopant. Thus, according to QTAIM, the incorporation of Mn atoms into the
basal plane of MoS2 catalytically activates all S atoms and three Mo neighboring the Mn dopant.

H.D. Morales-Rodríguez, K. Nguyen-Ba, F. Chen, Q. Shen, R. Tu, L.M. Zhang, F.L. Castillo-Alvarado, J.I. Rodríguez-Hernández, J.R. Vargas-Garcia, Modulating the electronic structure of MoS2 nanosheets by Mn doping for improving hydrogen evolution reaction: an experimental and theoretical DFT-QTAIM study, Materials Today Comm. 38, 107786 (2024)