Ultrafast synthesis of molybdenum carbide nanoparticles for efficient hydrogen generation

A facile and ultrafast synthesis of molybdenum carbide coated with few-layer carbon (MoC/C) has been developed, and the effect of reducing the thickness of the carbon coating on its catalytic activity in the hydrogen evolution reaction (HER) has been demonstrated. MoC/C produces a current density of 20 mA cm^-2 at an overpotential of 144 mV and a Tafel slope of 63.6 mV dec^-1 in 0.5 M H₂SO₄, and works stably under long-term electrolysis. MoC/C is one of the most active carbide electrocatalysts reported thus far, although MoC is not even the most active phase of molybdenum carbide and MoC/C has a small surface area. Complementary density functional theory calculations have afforded insight into this novel catalyst design, showing that increasing the thickness of the carbon layer leads to the composite system losing the characteristics of MoC and behaving more like a carbon surface, and thereby resulting in a reduction in HER activity.