Engineering MoS nanostructures from various MoO precursors towards hydrogen evolution reaction

MoS 2 -based nanomaterials are considered promising effective electrocatalysts to replace precious metal catalysts for hydrogen evolution reaction. However, understanding the effect of MoO 2 in MoS 2 -based catalysts for hydrogen evolution reaction is ambiguous. In this paper, MoS 2 nanoflowers of 210-430 nm in diameter were hydrothermally synthesized by the reduction of α-MoO 3 particles with KSCN in a hydrochloric acid medium. Similarly, MoO 2 -MoS 2 -B nanoflowers and MoO 2 -MoS 2 -R nanoflowers were fabricated using α-MoO 3 nanobelts and h-MoO 3 microrods as Mo sources, respectively. Systematic studies on synthetic parameters verified that the formation of MoS 2 nanoflowers is favored with high acidity, low MoO 3 /KSCN ratio and high temperature. The resultant nanoflowers served as electrocatalysts to drive hydrogen evolution in acidic solution. The MoS 2 nanoflowers showed a relatively higher activity with a potential of 256 mV at 10 mA cm −2 compared to MoO 2 -MoS 2 -B nanoflowers (283 mV) and MoO 2 -MoS 2 -R nanoflowers (305 mV). Furthermore, MoS 2 nanoflower catalysts maintained high stability after 1000 cycles and long-term durability for 5 h. The high catalytic activity could be ascribed to the large exposure of the Mo-S species and small amounts of Mo-O species on the MoS 2 -based catalyst surface. MoS 2 , MoO 2 -MoS 2 -B and MoO 2 -MoS 2 -R nanoflowers were prepared using α-MoO 3 particles, α-MoO 3 nanobelts and h-MoO 3 microrods, respectively; larger exposure of Mo-S and lower amounts of Mo-O were responsible for the higher HER performance.