Investigation on the Growth Mechanism of Cu2MoS4 Nanotube, Nanoplate and its use as a Catalyst for Hydrogen Evolution in Water

Cu2MoS4 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 Cu2MoS4 nanotube from (NH4)2MoS4 salt and Cu2O 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 Cu2MoS4 nanotube under hydrothermal treatment due to the Kirkendall effect or a selective etching of the Cu2MoS4 core. Extending the hydrothermal treatment causes a collapse of nanotube generating Cu2MoS4 nanoplate. The catalytic activities of these sulfides are investigated. The Cu2MoS4 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. Nanomagics! A mechanism is described for the growth of Cu2MoS4 nanotubes. Under ambient conditions, Cu2O and (NH4)2[MoS4]2− self‐assemble generating Cu(NH4)MoS4 nanorods. Subsequently, under the hydrothermal treatment, the Cu(NH4)MoS4 nanorods experience a selective corrosion where its core is dissolved generating Cu2MoS4 nanotubes. The latter collapses generating Cu2MoS4 nanoplates by further extending the hydrothermal treatment time. In a 0.5 M H2SO4 electrolyte solution, the Cu2MoS4 nanotubes and Cu2MoS4 nanoplates show promising H2‐evolving catalytic activities.