In situ O2-emission assisted synthesis of molybdenum carbide nanomaterials as an efficient electrocatalyst for hydrogen production in both acidic and alkaline media

Abstract

We report here a unique in situ O₂-emission assisted synthesis method to prepare molybdenum carbide (Mo_xC) nanomaterials with dense active sites and high effective surface area. The key to this protocol is the delicate design and synthesis of polymeric hybrid precursors by taking advantage of the synergy among the reactants. Oxidative polymerization of aniline (ANI) to form polyaniline (PANI), which acted as the nitrogen-rich carbon source, was initiated by adding aqueous H₂O₂ instead of the conventionally used ammonium persulfate (APS), and phosphomolybdate anions (PMo₁₂) were doped into the positively charged PANI matrix via coulombic interactions. During the polymerization, vigorous O₂ bubbles were in situ produced by H₂O₂ decomposition catalyzed by PMo₁₂, which mechanically broke down the precursor into nanosized polymeric hybrids with a porous and loose morphology. The Mo_xC electrocatalyst was optimized by varying the feeding content of PMo₁₂ and carbonization temperature, exhibiting remarkable catalytic activity and stability toward the hydrogen evolution reaction (HER) in both acidic and alkaline solutions. It requires an overpotential of only 144 mV and 141 mV to reach a current density of 10 mA cm⁻² in 0.5 M H₂SO₄ and in 1 M NaOH, respectively, making it among the best of the reported Mo_xC-based electrocatalysts.