Amorphous Molybdenum Sulfide on Three-Dimensional Hierarchical Hollow Microspheres Comprising Bamboo-like N-Doped Carbon Nanotubes as a Highly Active Hydrogen Evolution Reaction Catalyst

Novel amorphous-MoS_x-coated three-dimensional (3D) hierarchical hollow microspheres comprising one-dimensional bamboo-like N-doped carbon nanotubes (BNCNT/MoS_x-HM) are developed as a highly active electrocatalyst for the hydrogen evolution reaction (HER). The 3D hierarchical microspheres are easily prepared via the growth of bamboo-like N-doped CNTs (BNCNTs) on both the inner and outer surfaces of Co₃O₄-MgO/carbon hollow microspheres, which are prepared by spray pyrolysis, followed by uniform MoS_x coating of the surface. Metallic Co nanocrystals play a key role in the growth of BNCNTs, acting as catalysts for their nucleation. Owing to the electrostatic attraction between the N-doped sites in BNCNTs and the thiomolybdate precursor anions, few-layered amorphous MoS_x catalysts are well deposited on BNCNT surfaces, even at low temperature. The 3D hierarchical hollow structure facilitates electrolyte access, and the synergistic effect between the MoS_x catalyst material with ample active sites and the conductive N-doped CNTs increases electrochemical activity for the HER. Accordingly, electrochemical assessment of BNCNT/MoS_x-HM reveals a overpotential of 159 mV at a current density of 10 mA cm^-2, a low Tafel slope of 41.1 mV dec^-1, and excellent stability in acidic conditions.