Binary molten salt in situ synthesis of sandwich‐structure hybrids of hollow β‐Mo₂C nanotubes and N‐doped carbon nanosheets for hydrogen evolution reaction

Abstract Focused exploration of earth‐abundant and cost‐efficient non‐noble metal electrocatalysts with superior hydrogen evolution reaction (HER) performance is very important for large‐scale and efficient electrolysis of water. Herein, a sandwich composite structure (designed as MS‐Mo₂C@NCNS) of β‐Mo₂C hollow nanotubes (HNT) and N‐doped carbon nanosheets (NCNS) is designed and prepared using a binary NaCl–KCl molten salt (MS) strategy for HER. The temperature‐dominant Kirkendall formation mechanism is tentatively proposed for such a three‐dimensional hierarchical framework. Due to its attractive structure and componential synergism, MS‐Mo₂C@NCNS exposes more effective active sites, confers robust structural stability, and shows significant electrocatalytic activity/stability in HER, with a current density of 10 mA cm⁻² and an overpotential of only 98 mV in 1 M KOH. Density functional theory calculations point to the synergistic effect of Mo₂C HNT and NCNS, leading to enhanced electronic transport and suitable adsorption free energies of H* (ΔG_H*) on the surface of electroactive Mo₂C. More significantly, the MS‐assisted synthetic methodology here provides an enormous perspective for the commercial development of highly active non‐noble metal electrocatalysts toward efficient hydrogen evolution.