Hierarchical microsphere assembled by nanoplates embedded with MoS₂ and (NiFe)S _x nanoparticles as low-cost...

The development of low-cost electrocatalysts with high performance is important to provide sustainable hydrogen energy. In this work, via one-step sulfuration of [Formula: see text] intercalated NiFe-layered double hydroxide (abbr. NiFe-MoO₄-LDH), hierarchical microspheres are assembled by intersecting nanoplates (15-30 nm in thickness) which are then decorated with MoS₂ and (NiFe)S _x nanoparticles (∼25 nm in size). The NiFe-MoO₄-LDH is synthesized beforehand by a one-pot hydrothermal reaction. Under sulfuration at 300 °C, 400 °C and 600 °C, the NiFe-MoO₄-LDH transforms into multi-metal sulfides of NiFeMoS-T (T is applied temperature). During sulfuration, the confinement effect of LDH limits the growth of metal sulfides, causing formation of nanoparticles of MoS₂ and (NiFe)S _x to expose more catalytic active sites. In an alkaline medium, NiFeMoS-400 depicts superior performance for hydrogen evolution reaction (HER), giving an overpotential of 210 mV at 10 mA cm^-2. A Tafel slope of 88 mV dec^-1 indicates a mixed Volmer-Heyrovsky rate-determining step. The electrode also maintains long-term electrochemical durability during 15 h electrolysis at 25 mA cm^-2. The NiFe-MoO₄-LDH precursor owns three metal elements (Ni, Fe and Mo), which ensure the formation of polymetallic sulfides, and maximum utilization of the LDH layer and interlayer metals contributes to the optimal electrocatalytic activity. The NiFeMoS nanoassembly is a potential low-cost and high-efficiency electrocatalyst.