  Now-a-days, the development of clean and green energy sources is the prior
interest of research due to increasing global energy demand and extensive usage
of fossil fuels that create pollutants. Hydrogen has the highest energy density
by weight among all chemical fuels. For the commercial-scale production of
hydrogen, water electrolysis is the best method which in turn requires an
efficient, cost-effective and earth-abundant electrocatalyst. Recent studies
have shown that the 2D Janus TMDs are highly effective in the electrocatalytic
activity for HER. Herein we report a 2D monolayer WSeTe Janus TMD
electrocatalyst for HER. We studied the electronic properties of 2D monolayer
WSeTe Janus TMD using periodic DFT calculations, and the direct electronic band
gap was obtained to be 2.39 eV. After the calculations of electronic
properties, we explored the HER intermediates including various transition
state structures (Volmer TS, Heyrovsky TS, and Tafel TS) using a molecular
cluster model of WSeTe noted as W10Se9Te12. The present calculations revealed
that the 2D monolayer WSeTe Janus TMD is a potential electrocatalyst for HER.
It has the lowest energy barriers for all the TSs among other TMDs, such as
MoS2, Mn-MoS2, MoSSe, etc. The calculated Heyrovsky energy barrier (= 8.72
kcal.mol-1) for the Volmer-Heyrovsky mechanism is larger than the Tafel energy
barrier (=3.27 kcal.mol-1) in the Volmer-Tafel mechanism. Hence our present
study suggests that the formation of H2 is energetically more favorable via the
Vomer-Tafel mechanism. This work helps shed light on the rational design of
effective HER catalysts.
