Sulfur-Emission-Free Process of Molybdenum Carbide Synthesis by Lime-Enhanced Molybdenum Disulfide Reduction with Methane

Topochemical synthesis of low-dimensional nanomaterials

Over the past several decades, nanomaterials have been extensively studied owing to having a series of unique physical and chemical properties that exceed those of conventional bulk materials. Researchers have developed a lot of strategies for the synthesis of low-dimensional nanomaterials. Among them, topochemical synthesis has attracted increasing attention because it can provide more new nanomaterials by improving and upgrading inexpensive and accessible nanomaterials. In this review, we summarize and analyze many existing topochemical synthesis methods, including selective etching, liquid phase reactions, high-temperature atmosphere reactions, electrochemically assisted methods, etc. The future direction of topochemical synthesis is also proposed.

Epitaxial Synthesis of Molybdenum Carbide and Formation of a Mo2C/MoS2 Hybrid Structure via Chemical Conversion of Molybdenum Disulfide

The epitaxial synthesis of molybdenum carbide (Mo₂C, a 2D MXene material) via chemical conversion of molybdenum disulfide (MoS₂) with thermal annealing under CH₄ and H₂ is reported. The experimental results show that adjusting the thermal annealing period provides a fully converted metallic Mo₂C from MoS₂ and an atomically sharp metallic/semiconducting hybrid structure via partial conversion of the semiconducting 2D material. Mo₂C/MoS₂ hybrid junctions display a low contact resistance (1.2 kΩ·μm) and low Schottky barrier height (26 meV), indicating the material's potential utility as a critical hybrid structural building block in future device applications. Density functional theory calculations are used to model the mechanisms by which Mo₂C grows and forms a Mo₂C/MoS₂ hybrid structure. The results show that Mo₂C conversion is initiated at the MoS₂ edge and undergoes sequential hydrodesulfurization and carbide conversion steps, and an atomically sharp interface with MoS₂ forms through epitaxial growth of Mo₂C. This work provides the area-controllable synthesis of a manufacturable MXene from a transition metal dichalcogenide material and the formation of a metal/semiconductor junction structure. The present results will be of critical importance for future 2D heterojunction structures and functional device applications.

Topochemical synthesis of 2D materials

This review summarizes the rapidly-developed topochemical synthesis of 2D materials, explains the growth mechanisms and provides outlooks for future research.