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Unveiling the role of 2D monolayer Mn-doped MoS₂ material: toward an efficient electrocatalyst for H₂ evolution reaction
Publikationstyp
Journal Article
Date Issued
2022-02-07
Sprache
English
Author(s)
Institut
Volume
24
Issue
1
Start Page
265
End Page
280
Citation
Physical Chemistry Chemical Physics 24 (1): 265-280 (2022-01-07)
Publisher DOI
Scopus ID
PubMed ID
34881758
Publisher
RSC Publ.
Two-dimensional (2D) monolayer pristine MoS₂ transition metal dichalcogenide (TMD) is the most studied material because of its potential applications as nonprecious electrocatalyst for the hydrogen evolution reaction (HER). Previous studies have shown that the basal planes of 2D MoS₂ are catalytically inert, and hence it cannot be used directly in desired applications such as electrochemical HER in industry. Here, we thoroughly studied a defect-engineered Mn-doped 2D monolayer MoS2₂ (Mn-MoS₂) material, where Mn was doped in pristine MoS₂ to activate its inert basal planes. Using the density functional theory (DFT) method, we performed rigorous inspection of the electronic structures and properties of the 2D monolayer Mn-MoS₂ as a promising alternative to noble metal-free catalyst for effective HER. A periodic 2D slab of monolayer Mn-MoS₂ was created to study the electronic properties (such as band gap, band structures and total density of states (DOS)) and the reaction pathways occurring on the surface of this material. The detailed HER mechanism was explored by creating an Mn1Mo9S21non-periodic finite molecular cluster model system using the M06-L DFT method including solvation effects to determine the reaction barriers and kinetics. Our study revealed that the 2D Mn-MoS2follows the most favorable Volmer-Heyrovsky reaction mechanism with a very low energy barrier during H₂ evolution. It was found that the change in the free energy barrier (ΔG) during the H˙-migration (i.e., Volmer) and Heyrovsky reactions is about 10.34-10.79 kcal mol−1(computed in the solvent phase), indicating that this material is an exceptional electrocatalyst for the HER. The Tafel slope (y) was lower in the case of the 2D monolayer Mn-MoS₂ material due to the overlap of the s-orbital of hydrogen and d-orbitals of the Mn atoms in the HOMO and LUMO transition states (TS1 and TS2) of both the Volmer and Heyrovsky reaction steps, respectively. The better stabilization of the atomic orbitals in the HER rate-limiting step Heyrovsky TS2 is the key for reducing the reaction barrier, and thus the overall catalysis, indicating a better electrocatalytic performance for H2evolution. This study focused on designing low-cost and efficient electrocatalysts for the HER using earth abundant transition metal dichalcogenides (TMDs) and decreasing the activation energy barriers by scrutinizing the kinetics of the reaction to achieve high reactivity.
DDC Class
530: Physik
540: Chemie
More Funding Information
This work was financially supported by the Science and Engineering Research Board-Department of Science and Technology (SERB-DST), Government of India under the Grant No. ECR/2018/000255. Dr Srimanta Pakhira thanks the Science and Engineering Research Board, Department of Science and Technology (SERB-DST), Govt. of India for providing his highly prestigious Ramanujan Faculty Fellowship under the scheme no. SB/S2/RJN-067/2017, and for his Early Career Research Award (ECRA) under the grant no. ECR/2018/000255.