Molybdenum sulfide/N-doped CNT forest hybrid catalysts for high-performance hydrogen evolution reaction

Cost effective hydrogen evolution reaction (HER) catalyst without using precious metallic elements is a crucial demand for environment-benign energy production. Molybdenum sulfide is one of the promising candidates for such purpose, particularly in acidic condition, but its catalytic performance is inherently limited by the sparse catalytic edge sites and poor electrical conductivity. We report synthesis and HER catalysis of hybrid catalysts composed of amorphous molybdenum sulfide (MoS_x) layer directly bound at vertical N-doped carbon nanotube (NCNT) forest surface. Owing to the high wettability of N-doped graphitic surface and electrostatic attraction between thiomolybdate precursor anion and N-doped sites, ∼2 nm scale thick amorphous MoS_x layers are specifically deposited at NCNT surface under low-temperature wet chemical process. The synergistic effect from the dense catalytic sites at amorphous MoS_x surface and fluent charge transport along NCNT forest attains the excellent HER catalysis with onset overpotential as low as ∼75 mV and small potential of 110 mV for 10 mA/cm² current density, which is the highest HER activity of molybdenum sulfide-based catalyst ever reported thus far.