Layered Nano‐Mosaic of Niobium Disulfide Heterostructures by Direct Sulfidation of Niobium Carbide MXenes for Hydrogen Evolution

Abstract MXene‐transition metal dichalcogenide (TMD) heterostructures are synthesized through a one‐step heat treatment of Nb 2 C and Nb 4 C 3 . These MXenes are used without delamination or any pre‐treatment. Heat treatments accomplish the sacrificial transformation of these MXenes into TMD (NbS 2 ) at 700 and 900 °C under H 2 S. This work investigates, for the first time, the role of starting MXene phase in the derivative morphology. It is shown that while treatment of Nb 2 C at 700 °C leads to the formation of pillar‐like structures on the parent MXene, Nb 4 C 3 produces nano‐mosaic layered NbS 2 . At 900 °C, both MXene phases, of the same transition metal, fully convert into nano‐mosaic layered NbS 2 preserving the parent MXene's layered morphology. When tested as electrodes for hydrogen evolution reaction, Nb 4 C 3 ‐derived hybrids show better performance than Nb 2 C derivatives. The Nb 4 C 3 ‐derived heterostructure exhibits a low overpotential of 198 mV at 10 mA cm −2 and a Tafel slope of 122 mV dec −1 , with good cycling stability in an acidic electrolyte.