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.
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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)Key conceptsBAND bonding analysis catalysis materials science nanoscience periodic DFT Relativistic DFT