Molten salt-assisted controlled synthesis of two-dimensional molybdenum carbide

The present investigation examines the carbothermal reduction synthesis of two-dimensional molybdenum carbide (2D Mo2C) using sodium carbonate (Na2CO3) as a molten salt diffusion promoter and sodium sulfide (Na2S) as a solid-state intercalation agent. Raw molybdenum disulfide (MoS2) powder undergoes carbothermal reduction facilitated by activated carbon and Na2CO3 above 800 degrees C to produce 2D Mo2C layers intercalated by Na2S. The diffusion of Na2S can be enhanced by the fluidity of molten salt Na2CO3, leading to the expansion of the Mo2C layer spacing to 29 nm under the influence of the temperature field. Na2S intercalation prevents layer shrinkage during cooling while molten Na2CO3 directs 2D growth, yielding 10 nm-thick sheets. The product maintains hexagonal beta-Mo2C structure up to 950 degrees C with microflowers of accordion-shaped nanosheets. Ultrasonication exfoliates the weakly bound Mo2C layers into uniform, freely suspended flakes around 10-100 nm in lateral size. This work demonstrates the tuning of 2D Mo2C morphology in high-temperature reactions by utilizing molten salts. The principal results are the synthesis of micrometer-sized Mo2C sheets with controlled nanoscale thickness and uniform nanosheet dispersions, enabled by molten salt-directed diffusion of intercalated species. The major conclusion drawn is that solid-liquid synergistic diffusion can guide precision synthesis of layered nanomaterials.