Basal Plane Activation in Monolayer MoTe2 for Hydrogen Evolution Reaction via Phase Boundaries

Two-dimensional transition metal dichalcogenides (2D TMDCs) have attracted tremendous interest as one prominent material group promising inexpensive electrocatalysts for hydrogen evolution reaction (HER). In the present study, using monolayer MoTe₂ 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 in energetically stable phase boundaries, as potential catalytic centers for HER, all indicating enhanced HER activity than 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 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 towards designing new class of high-performance HER electrocatalysts based on 2D TMDCs.