Phase-dependent intermediate adsorption regulation on molybdenum carbides for efficient pH-universal hydrogen evolution

Molybdenum carbides are the most promising noble metal-free electrocatalyst for hydrogen evolution reaction (HER). However, the investigation of phase-dependent intermediate adsorption on phase evolution engineering of molybdenum carbides is still insufficient. Herein, we developed a phase evolution carbonization procedure for synthetic molybdenum carbides with tunable phases for efficient hydrogen production, whose hydrogen inter-mediate adsorption energies can be regulated. Among them, Mo2C/MoC-1 shows a lowest overpotential of 128 mV, 162 mV and 119 mV in acidic, neutral and alkaline environment, respectively, steady operating at 10 mA cm-2 for 100 h. Tunable phase composites of molybdenum carbide composites induce favorable electronic structure and a local nucleophilic/electrophilic region at the interface of alpha-MoC and P-Mo2C phases, which promotes their HER performance. Density functional theory (DFT) calculations further reveal that Mo2C/MoC-1 conveys a Hads adsorption free energy (Delta GH*) of-0.17 eV in acid and a low water dissociation energy barrier of 1.12 eV in alkaline and neutral environment, pledging admirable HER performance in pH-universal conditions. This work provides a guidance to modulate the phase of molybdenum carbides for hydrogen evolution.