Controllable and universal anisotropic vapor–solid growth of vertical 2D metal chalcogenide nanoflakes with enhanced photoelectric and electrocatalytic properties

Abstract

Epitaxial growth and subsequent processing of 2D materials are mostly confined to xy plane parallel to the substrate. Introducing another degree of freedom, i.e., the vertical direction perpendicular to the base plane, is very intriguing, as the resulting vertically aligned 2D materials will intuitively have a high aspect ratio, anisotropic structure, and abundant edge sites, holding great promise in field emission, photoelectronics, piezoelectricity, clean energy catalysis, etc. However, the key factors governing the spatially anisotropic growth to selectively obtain vertically or horizontally aligned 2D nanoflakes remain elusive. Herein, we report a controllable and general strategy to vertically grow representative 2D metal chalcogenide materials, including but not limited to SnS, SnSe, Bi2Se3, MoO3, and MoS2 nanoflakes, via a rapid heating–cooling process on various optional substrates. The rapid heating–cooling process allows rapid desublimation and nucleation of highly-supersaturated precursor vapor, leading to ultrafast growth of vertically aligned nanoflakes with exposed side surfaces and edges. As an example, the vertically grown SnS nanoflakes exhibit anisotropic spectroscopic features, superior photoelectric properties and enhanced electrocatalytic performances for the nitrate reduction and CO2 reduction reactions. This work provides a feasible approach to controllably synthesize versatile vertically aligned 2D metal chalcogenide nanoflakes on various substrates, which can advance the mechanistic understanding of anisotropic growth and physicochemical properties of 2D materials towards photoelectric devices and clean energy conversion.