Vapor–Liquid–Solid Growth of Thin and Epitaxial Transition Metal Nitride Nanosheets for Catalysis and Energy Conversion

Transition metal nitrides (TMNxs) present noble metal-like properties and thus are considered important functional materials for catalysis and energy conversion applications. However, obtaining well-defined thin and epitaxial nitrides remains challenging, in contrast to the facile production of high-quality graphene and other 2D atomic crystals. Here, we report vapor–liquid–solid (VLS) growth of thin MoN nanosheets with molten Na2MoO4 employed as the Mo source and NH3 as the nitriding gas. Single-crystalline and micrometer-sized thin and epitaxial MoN nanosheets with a controllable phase can be obtained on Al2O3(0001) and other single crystals in which the Na-containing liquid precursor and the liquid–solid interface play important roles in epitaxial growth. We further demonstrate the facile preparation of other high-quality thin and epitaxial TMNx nanosheets, including WN, CrN, and VN, thereby suggesting the universality of the VLS route for the growth of thin and epitaxial nitride and carbide overlayers. Our work provides an ideal model structure for the study of catalytic mechanisms.