Modulating the Electronic Structure and In-Plane Activity of Two-Dimensional Transition Metal Dichalcogenide (MoS2, TaS2, NbS2) Monolayers by Interfacial Engineering

摘要

Two-dimensional transition metal dichalcogenides (2D-TMDs) are a unique class of functional nanomaterials with appealing electronic and electrocatalytic properties, and substrate-induced interface engineering offers a useful tool for further modification. Here from first-principles calculations we investigated the electronic structures and electrocatalytic activities of four representative 2D-TMD single layers (2H-MoS2, 1T'-MoS2, 2H-NbS2, 2H-TaS2) supported on metals (Au(111), Cu(111), Mo(110)) and 2D substrates (graphene, hexagonal boron nitride (h-BN)). The investigated 2D-TMDs yield weak physisorption on graphene/h-BN and partial to strong covalent bonding on metals (Au(111) < Cu(111) < Mo(110)). In particular, metallic 1T'-MoS2, 2HNbS(2), and 2H-TaS2 exhibit interface binding stronger than the semiconducting 2H-MoS2. Analyses of the electronic structures indicate strong Fermi level pinning of 2H-MoS2 by the metal contact, leading to a small or vanishing n-type Schottky barrier. The metallic 2D-TMDs are also strongly modified by the downshift and broadening in the electronic states. Using H adsorption as the testing probe, we further demonstrated the intrinsic activity of 2D-TMDs is well retained on graphene/h-BN, while the metal substrates can substantially alter the surface reactivity, resulting in enhanced H-S binding on the semiconductor 2H-MoS2 and contrasting weakened H adsorption over metallic 1T'-MoS2, 2H-NbS2, and 2H-TaS2. The electronic effect and geometric effect appear to play an important role in the activity modulation. These findings highlight a fundamental difference in the influence of heterocontacts on the in-plane reactivity of semiconducting and metallic 2D-TMDs, which would provide the guideline for selecting the optimal substrate for electronic and catalytic applications of different 2D-TMDs.