Carbon-Based Metallic Cobalt Pyrite Nanotubes as Stable Electrode Materials for Electrochemical Hydrogen Evolution

Transition metal dichalcogenides (TMDs) have attracted tremendous research attention because of their potential performance in the electrochemical hydrogen evolution reaction. Also, the three-dimensional (3D) hollow structure can provide additional excellent electrochemical activities. Here, we report for the first time that a carbon-based metallic cobalt pyrite (C@CoS2) hollow tubelike structure (nanotubes) can be achieved by a sulfuration process. This process adopts a simple one-step chemical vapor diffusion-controlled strategy, and the growth of nanotubes can be adjusted by simply changing the gas reaction condition. The obtained C@CoS2 nanotubes have an outstanding electrocatalytic performance. The results show the overpotential (220 mV) and Tafel slope (55.04 mV dec–1) of C@CoS2 nanotubes are much lower than those of C@CoS2 nanorods (slightly higher than the Pt electrode) when the cathode current density is 10 mA cm–2. Additionally, the current density of the C@CoS2 electrode does not decrease much at an overpotential of −250 mV (vs the reversible hydrogen electrode, RHE) after a 36 h test, demonstrating a good durability. The hollow structure of the nanotubes plays a key role in the hydrogen evolution reaction (HER), the polyporous carbon materials work for improving the conductivity, and exposed active sites increase the catalytic activity, which together enhance the whole HER activities. The facile strategy may provide an alternative to prepare other multifunctional TMD nanomaterials for water splitting or other electrochemical reactions.