Molten salts assisted one-pot synthesis of hollow transition metal carbides

Hollow transition metal carbides (TMCs) have broad potential applications due to their high melting point, low density, high specific surface area, and good electrical conductivity. However, the conventional preparation of TMCs often involves complex processes and requires high temperature, which limits their practical application. Herein, hollow TMC powders including NbC, VC, ZrC, and TiC were successfully prepared by one-pot molten salt synthesis (MSS) at relatively low temperatures. The formation mechanism and the influence of carbon crystallinity on the synthesis process were investigated. It was found that amorphous carbon precursors act as sacrificial templates in MSS, which can induce the Kirkendall effect to form the hollow structure. When using graphitized carbon microspheres as carbon precursors, the reaction between transition metals and carbon is uneven and relatively sluggish, which prevents the occurrence of the Kirkendall effect, thus hindering the formation of hollow structure. This work provides a facile method to prepare hollow TMCs with the advantages of low synthesis temperature and adjustable morphology.