Flash Thermal Shock Synthesis of Heterostructured Transition Metal Dichalcogenides and Carbides in Milliseconds

Abstract Transition metal dichalcogenides (TMDs) offer remarkable potential for next‐generation functional devices, but achieving ultrafast synthesis with precise structural and phase control under ambient conditions remains a significant challenge. Here, ultrafast photothermal annealing assisted by graphene oxide is introduced for precise phase control of TMDs forming a heterostructure. This process reaches adjustable temperatures between 1 768 and 3 162 K within 10 ms, featuring rapid kinetics, enabling the synthesis of various metastable nanomaterials in ambient air. The TMDs form directly from precursors above 1 700 K, while temperatures above 2 300 K induce carbothermic reactions, producing metastable transition metal carbides (TMCs) and core@shell heterostructures (TMC@TMD and TMC@carbon). Introducing seed materials like single metals, metal oxides, and multielement/high‐entropy alloys enables the formation of core(seed)@shell (TMD) heterostructures. The resulting composites demonstrated significantly enhanced catalytic performance in gas sensing and hydrogen production. This robust and versatile photothermal annealing method holds broad potential for designing advanced heterostructure‐engineered TMD and/or TMC composites tailored for targeted applications.