Poster Presentation 28
First Principle DFT Study of Activation Energy for H2
Evolution in MoS2, WS2 and WxMo1-xS2
1
Srimanta Pakhira1 and Jose L. Mendoza-Cortes1,2*
Department of Chemical & Biomedical Engineering, FAMU-FSU College of Engineering,
Florida State University, Tallahassee, Florida, USA
2
Scientific Computing Department, Materials Science and Engineering Program, High Performance Materials Institute, Condensed
Matter Theory, National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, USA
Abstract
The design and development of inexpensive highly efficient catalysts for hydrogen production, underpins
several emerging clean-energy technologies and chemical engineering. Recently molybdenum disulfide
(MoS2) [1] and tungsten disulfide (WS2) [2] clusters and bulk materials have been attracted a great attention
as an emerging material for electrochemical hydrogen evolution reaction (HER) catalyst. Here we have
computationally designed a new type of cluster, WxMo1-xS2 substituting either Mo atoms by W atoms in
MoS2 cluster or W atoms by Mo atoms in WS2 cluster using ab initio DFT method (here M06L), and we have
found the catalytic activity of the cluster has been increased due to the substitution/doping. In the
computation, we have used 6-31+G** basis sets for H, S, and O atoms, as well as LANL2DZ basis sets with
effective core potentials (ECP) for Mo and W atoms. Our computational study reveals that the W 0.4M0.6S2
cluster has the lowest activation energy barrier for H2 evolution, about 4.40 kcal mol-1 in gas phase, and 10.31
kcal mol-1 in solvent phase (water) with four explicit water molecules as shown in Figure 1 and Figure 2.
Hydronium protonation of the hydride on the Mo site is about 21.67 kcal/mol in MoS2, and it is about 20.17
kcal mol-1 on the W site in WS2. We predict the Volmer-Tafel mechanism in which hydrogen atoms bound to
tungsten and sulfur sites recombine to form H2 has a barrier of 10.31 kcal mol-1 in the W0.4M0.6S2 cluster. The
W0.4M0.6S2 cluster shows the highest catalytic activity among the three clusters.
Energy Barrier in kcal mol-1
22
Gas Phase Heyrovsky
Solvent Phase Heyrovsky
20
18
16
14
12
10
8
6
4
MoS2
Figure 1.
-
W0.4Mo0.6S2
-
WS2
-
Figure 2.
References
1. Huang Y, Nielsen RJ, Goddard III WA, Soriaga MP. 2015. The reaction mechanism with free energy barriers for electrochemical
dihydrogen evolution on MoS2. J. Am. Chem. Soc. 137:6692.
2. Voiry D, Yamaguchi H, Li J, Silva R, Alves DC, Fujita T, Chen M, Asefa T, Shenoy VB, Eda G, Chhowalla, M. 2013. Nat. Mat.
12:850.
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