Investigation on the Growth Mechanism of Cu 2 MoS 4 Nanotube, Nanoplate and its use as a Catalyst for Hydrogen Evolution in Water

Cu2 MoS4 is a ternary transition-metal sulfide that shows great potential in the field of energy conversion and storage, namely catalytic H2 evolution in water and Li-, Na- or Mg-ion battery. In this work, we report on a growth mechanism of the single-crystalline Cu2 MoS4 nanotube from (NH4 )2 MoS4 salt and Cu2 O nanoparticle. By probing the nature and morphology of solid products generated in function of reaction conditions we find that the crystalline Cu(NH4 )MoS4 nanorod is first generated at ambient conditions. The nanorod is then converted into Cu2 MoS4 nanotube under hydrothermal treatment due to the Kirkendall effect or a selective etching of the Cu2 MoS4 core. Extending the hydrothermal treatment causes a collapse of nanotube generating Cu2 MoS4 nanoplate. The catalytic activities of these sulfides are investigated. The Cu2 MoS4 shows superior catalytic activity to that of Cu(NH4 )MoS4 . Catalytic performance of the former largely depends on its morphology. The nanoplate shows superior catalytic activity to the nanotube, thanks to its higher specific electrochemical surface area.