Reconstructed edges of T phase transition metal dichalcogenides

As surfaces are to bulk materials, edge configurations greatly influence the properties and ensuing applications of two-dimensional (2D) materials. Being a large family of "beyond graphene", 2D transition metal dichalcogenides (TMDCs) have many potential applications due to diverse phases and tunable properties. Unlike the well-studied H phase TMDCs initiated by MoS2, the edge structures of T phase TMDCs remain poorly studied. Herein, taking freestanding T phase PtSe2 as a prototype, we rationally construct 43 edge structures on the basis of conventional zigzag (ZZ) and armchair (AC) edges, and systematically evaluate their thermodynamic stabilities and relevant properties using density functional theory. Twelve most stable reconstructed edges (five ZZ-oriented and seven AC-oriented) are found to be highly stable at different experimental conditions, which can be achieved by precise control of synthesis conditions. Further Wulff constructions suggest hexagonal shapes with ZZ edges would be the equilibrium structures of the freestanding T phase PtSe2 clusters or quantum dots. Electronic structure calculations show tunable band gap via edge reconstruction. Some reconstructed edges also exhibit excellent catalytic activity for hydrogen evolution reaction. Our work is expected to advance the knowledge of edge structures of T-phase TMDCs, and motivates materials design via TMDC edge engineering. (C) 2021 Elsevier Ltd. All rights reserved.