Basal plane activation in monolayer MoTe(2)for the hydrogen evolution reactionviaphase boundaries

Two-dimensional transition metal dichalcogenides (2D TMDCs) have attracted tremendous interest as a prominent material group providing inexpensive electrocatalysts for the hydrogen evolution reaction (HER). In the present study, using monolayer MoTe(2)as a representative, we demonstrated that phase boundaries can provide a viable pathway to activate the basal plane of 2D TMDCs for enhanced HER performance. Comprehensive first-principles calculations have been performed to examine the energetics and structural stabilities of possible 2H/1T ' phase boundary configurations. Three categories of sites, Te, Mo and hollow sites, have been identified at energetically stable phase boundaries, as potential catalytic centers for the HER, all indicating enhanced HER activity compared to that of the pristine basal lattice. In particular, the hollow sites, a new group of sites induced by phase boundaries, show great promise by exhibiting a Gibbs free energy (Delta G(H)) near the thermoneutral value for hydrogen adsorption, comparable to that of Pt. The mechanisms underlying hydrogen adsorption at phase boundaries were then revealed, shown to be attributed to the unique local hydrogen adsorption geometries and electronic structures at phase boundaries. Our study clarifies the important mechanistic aspects underlying hydrogen activation at phase boundaries, providing valuable theoretical insights into designing a new class of high-performance HER electrocatalysts based on 2D TMDCs.