Engineering of MoSe and WSe Monolayers and Heterostructures by DFT-Molecular Dynamics Simulations.

Herein, comprehensive modeling and investigation of bulk, monolayers, and heterostructures of 2D transition metal dichalcogenides (TMDs) MoSe and WSe have been provided by state-of-the-art spin-polarized density functional theory (DFT) simulations. This work aims to support the rational design of TMD-based (photo)electrocatalysts for water splitting by incorporating a more realistic description of the catalyst-electrolyte interface. Unlike conventional static or implicit-solvent models, an explicit water environment has been considered at the interface with MoSe and WSe monolayers and heterostructures, moving beyond the usual idealized vacuum modeling. Our approach allows for explicit, atomistic interactions at the catalyst-liquid interface at a given temperature, revealing a more realistic modeling and dynamic assessment of interfacial structures. Our simulations reveal that both MoSe and WSe exhibit water-repellent behavior, yet preferential hydrogen bonding emerges at specific surface sites. These localized interactions may enhance the catalytic surface activity, underscoring the relevance of capturing interfacial water dynamics in computational models. The study underscores the importance of accounting for explicit liquid water dynamics in DFT-based investigations aiming to engineer monolayer/heterostructure catalytic properties accurately. Here, the key ability to simulate and analyze realistic aqueous environments interacting with semiconducting 2D materials allowed predicting and tuning key interfacial properties, such as electronic structure, water organization, surface electric field, and work function, for the engineering and modeling of enhanced MoSe and WSe-based interfaces. The lattice parameters, bulk modulus, and electronic structure were also investigated for bulk MoSe and WSe, which yielded results that are in agreement with the available experimental data. Overall, our study demonstrates that realistic, temperature-dependent simulations of solid-liquid interfaces provide critical insight into the physicochemical behavior of 2D semiconducting catalysts. A similar approach can be applied to other complex facets and interfaces of interest and, hence, possibly help in the design of novel catalysts.