Mo2C@NC nanowire bundle for efficient electrocatalytic hydrogen evolution

Abstract

We demonstrate a novel route for the shape-controlled synthesis of inorganic-organic hybrid nanowire bundle of Mo2C and N-doped carbon (Mo2C@NC) for the electrochemical hydrogen evolution reaction (HER) in acidic and alkaline medium. The synthetic procedure involves the facile complexation of Mo precursor, molybdate, with cationic polymer, poly (diallyldimethylammonium chloride) (PDDA) and the subsequent carburization at 800 °C under optimized condition. The Mo2C@NC nanowire bundle has an average diameter of 75 nm and length of 2.5–4 μm. It has > 67% pyridinic nitrogen and the Mo2C nanowires are coated with N-doped carbon of 2–5 nm thickness. The annealing temperature has large control over the morphology and chemical composition. The electrocatalytic activity of Mo2C@NC is examined in acidic and alkaline solution. The benchmark current density of 10 mA/cm2 in acidic and alkaline pH at overpotential of 135 and 121 mV, respectively. Tafel slope of 61 and 56 mV/dec was obtained in acidic and alkaline pH, respectively. The electrocatalytic HER involves Volmer-Heyrovsky mechanism. The hybrid material has outstanding durability in acidic pH and it retains its initial activity even after 1000 extensive repeated potential cycles. The post-HER analysis reveals that the integrity of Mo2C@NC does not change in acidic pH. The superior performance can be explained by considering the surface morphology of Mo2C and the synergistic effect between the carbide catalyst and N-doped carbon.