Phase Engineering of Molybdenum Carbide via Vanadium Doping for Boosted Hydrogen Evolution Reaction in Water Electrolysis

Efficient and low-cost electrocatalysts play a crucial role in hydrogen production through electrolysis of water. Molybdenum (Mo) carbide with a similar electronic structure to Pt was selected, both α-MoC_1−x and α-MoC_1−x/β-Mo₂C electrocatalysts were successfully fabricated for electrochemical hydrogen evolution. A continuous optimization of the hydrothermal and carbonization conditions was carried out for the preparation of α-MoC_1−x. The biphasic molybdenum carbide catalysts were further achieved via vanadium doping with a phase transition of molybdenum carbide from α to β, which increases the specific surface area of the electrocatalyst. It was found that the V-Mo_xC catalyst obtained at a Mo/V molar ratio of 100:5 exhibited the best hydrogen production performance, with a β to α phase ratio of 0.827. The overpotential of V-Mo_xC at η₁₀ decreased to 99 mV, and the Tafel slope reached 65.1 mV dec⁻¹, indicating a significant improvement in performance compared to undoped samples. Excellent stability was obtained of the as-prepared electrocatalyst for water splitting over 100 h at a current density of 10 mA cm⁻².