One-step synthesis of Co9S8@Ni3S2 heterostructure for enhanced electrochemical performance as sodium ion battery anode material and hydrogen evolution electrocatalyst

In this work, sheet-like Co 9 S 8 was directly grown on Ni 3 S 2 spheres (donate as Co 9 S 8 @Ni 3 S 2 ) via a one-step hydrothermal synthetic approach. The structural characterization of Co 9 S 8 @Ni 3 S 2 revealed that the Co 9 S 8 nanosheets were perpendicularly arrayed on Ni 3 S 2 spheres. This heterostructure thus fixes the two-dimensional Co 9 S 8 in position on Ni 3 S 2 spheres to obtain a stable heterostructural material. Due to the strengthened morphological structure, high surface area, metallic feature of Co 9 S 8 and Ni 3 S 2 , and the synergetic effect, the Co 9 S 8 @Ni 3 S 2 showed excellent performance in sodium ion battery (SIB) anode and HER cathode. The electrochemical tests showed that Co 9 S 8 @Ni 3 S 2 can demonstrate excellent HER catalytic activity with only −0.16 ​V and −0.23 ​V overpotential needed to achieve 10 ​mA ​cm −2 and 100 ​mA ​cm −2 current density in acidic condition. Besides, Co 9 S 8 @Ni 3 S 2 heterostructure as an anode in SIB also delivered high discharge capacity of 699 ​mAh g −1 at 0.5 ​A ​g −1 current density in the first cycle, with 92% Columbic efficiency.