Molten Salt One-Pot Electrosynthesis of a Ni-MoC-Mo₂C/Mo Self-Supported Electrode for Efficient pH-Universal Hydrogen Evolution

Mo 2 C is expected to replace commercial Pt/C in hydrogen evolution reactions, but the strong Mo–H bond constrains the desorption of H* (H proton), blocking its activity. Herein, we design a one-pot synthesis method of a Ni-MoC-Mo 2 C/Mo self-supported electrode (SSE) in molten salts using CO 2 as a carbon source. The Ni doping and in situ construction of the MoC-Mo 2 C heterophase can balance the adsorption and desorption of H* on the Mo active site and significantly improve the catalytic activity. The as-obtained Ni-MoC-Mo 2 C/Mo has remarkable HER activity in three kinds of media. In particular, the η 10 (overpotential at 10 mA/cm 2 ) and η 100 (overpotential at 100 mA/cm 2 ) of Ni-MoC-Mo 2 C/Mo are only 35 and 113 mV in 1 M KOH and 73 and 153 mV in 0.5 M H 2 SO 4 . Besides, its η 10 is 301 mV, lower than that of Pt/C, in 1 M Na 2 SO 4 . Under the industrial current densities (≥200 mA/cm 2 ), its activity reveals remarkable stability during 24 h stability tests in 1 M KOH and 0.5 M H 2 SO 4 . The unique self-supporting structure of Ni-MoC-Mo 2 C/Mo shows the best hydrophilicity, which promotes bubble separation and improves the active site area between the catalytic layer and electrolyte. DFT calculations show that Ni-MoC-Mo 2 C/Mo has the closest free energy to zero (Δ G H* = −0.12 eV), facilitating the desorption of H* from the Mo active site.