Synthesis of two-dimensional N-terminated molybdenum carbides using an alloying strategy in molten salt

Abstract

Molybdenum carbide (Mo₂CT_x) has an electronic structure similar to that of platinum, thereby making it a promising non-precious-metal catalyst. However, preparing Mo₂CT_x efficiently and rapidly using a conventional redox method is challenging owing to the high exfoliation energy of the Mo₂Ga₂C precursor. In this study, a novel alloying method was developed to etch Ga rapidly from its precursor. The etching process was conducted in a LiCl–KCl molten salt containing Li₃N and an iron triad element (Fe, Co, or Ni). Here, Ga formed an alloy with the iron triad element, thereby reducing the reaction energy barrier and promoting the kinetics of Ga etching. Simultaneously, adding Li₃N to the molten salt created a specific N ion as a stable functional group adsorbed on the surface of Mo₂C. This nitrogen functional group (–N) optimizes the electronic structure of surface molybdenum by inducing strong covalent bonds. Consequently, the synthesized N-terminated Mo₂CT_x demonstrates superior electrocatalytic oxygen evolution activity to conventional F-terminated Mo₂CT_x and commercial IrO₂ in a 1 M KOH solution.