Ultrathin MoS₂ Nanosheets Vertically Grown on CoS₂ Acicular Nanorod Arrays: A Synergistic Three-Dimensional Shell/Core Heterostructure for High-Efficiency Hydrogen Evolution at Full pH

A three-dimensional (3D) MoS2/CoS2 composite with shell/core heterostructure is in situ synthesized, which is composed of CoS2 acicular nanorod arrays and edge-terminated MoS2 nanosheets vertically grown on each CoS2 nanorod. Benefiting from the epitaxial growth of 2H-MoS2 on the surface of CoS2, the edge planes of ultrathin MoS2 nanosheets are significantly exposed. Due to the structural properties, a large number of direct contact areas are formed between MoS2 and CoS2, and a strong interaction between these two phases causes the electrons at the interface to be redistributed. Owing to the synergy of MoS2 and CoS2, significantly increased MoS2 edge sites, and improved mass transfer and electron transport, MoS2/CoS2 exhibits a remarkable catalytic ability for hydrogen evolution reaction (HER) at full pH. In 1.0 M KOH, 1 M PBS (pH = 7.0), and 0.5 M H2SO4, the overpotential at a current density of 10 mA cm–2 is 97, 196, and 126 mV, with Tafel slope of 78.7, 77.5, 42.6 mV dec–1, respectively. In addition to reporting a promising HER catalyst, this work will also provide a meaningful reference for designing 3D nanocatalysts.