Ni-Assisted Low Temperature Synthesis of MoC_x with Enhanced HER Activity

Here we report a novel one-pot approach to synthesize MoC_x catalysts at much lowered temperature for hydrogen evolution reaction (HER) in acidic solution. A room-temperature co-precipitation reaction among Ni²⁺, MoO₄ ²⁻ and 2-methylimidazole in an aqueous solution produced a Mo−Ni−imidazole complex, which was used as the precursor to fabricate MoC_x. The morphological and chemical properties of the obtained MoC_x affected by calcination and other additive metal sources (like Fe, Co, Cu) were investigated in detail. We demonstrated that Ni−Mo alloying took place prior to MoC_x formation during heating, which catalyzed the crystallization of MoC_x at relatively low temperature. The MoC_x/Ni-650 catalyst exhibited a quite low overpotential of 172 mV at 20 mA cm⁻². The high performance originates from the synergistic effect between MoC_x and Ni−Mo alloy, high ratio of Mo³⁺/Mo²⁺, as well as high electrochemically active surface area and low charge-transfer resistance. This work would open a new way to the design and fabrication of other transition-metal carbide catalysts.