Investigation of structure and dynamics of water confined between hybrid layered materials of graphene, boron nitride, and molybdenum disulfide

Two-dimensional (2D) materials like graphene, boron nitride, and molybdenum disulfide are utilized in diverse applications including catalysis, sensing, energy storage, biology, electronics, and so on. However, on a number of occasions, these 2D materials may not satisfy all the desired functions individually due to limitations in their properties. Thus, the urgency to generate new materials by combining and/or functionalizing these pure materials has emerged as a need of the current hour. The hybridization aids in cherishing a blend of new properties by a combination of pure materials. However, the performance of these materials in most of these applications also strongly depends on surrounding environmental factors like temperature, pressure, and especially humidity. Thus, understanding the structure of water near these hybrids and their interfaces is critical to facilitate the design of new devices with enhanced performance. Here, we have computationally designed novel layered hybrid materials of 2D sheets of graphene, boron nitride, and molybdenum disulfide by stacking them one above another. Subsequently, the structure of water in the vicinity of sheets and confined between them was studied using all-atom (AA) molecular dynamics (MD) simulations. In order to understand the dynamics of water, sheets were modeled as flexible or rigid. The structural and dynamical characteristics of hybrids and water confined between these sheets were analyzed by employing radial distribution function (RDF), average atomic-density (z-density) profile of oxygen atoms, orientational tetrahedral order (OTO), asphericity of the Voronoi cell (AVC), O–H bond orientation of water molecules, mean squared displacement (MSD), and residence time probability (Pres(t)). Based on a visual inspection and in-depth analyses on the behavior of sheets when modeled as flexible, all water molecules confined between these sheets were eliminated due to stronger interactions between sheets and their disliking toward the water. Further, in the hybrids with sheets fixed at their crystallographic positions, structural and dynamical properties of water suggest that the hydrophilic interface of BN-MoS2 followed by BN-GR and GR-MoS2 favored the stable and ordered structure of water.