Sulfur bridges between Co9S8 nanoparticles and carbon nanotubes enabling robust oxygen electrocatalysis

Abstract

Electrocatalytic active species, for example, metal sulfides, have been widely combined with carbon nanomaterials for enhanced performance because of the synergetic effect arising from the interaction between different components. However, the binding between metal sulfides and carbon nanomaterials, which plays a key role in determining their interaction, has not been clearly elucidated. Herein, we reported the sulfur bridges between sulfur-doped carbon nanotubes (S-CNTs) and Co9S8 nanoparticles and their significant effect on the practical electrochemical performance. Compared to the physically mixed composites, the one with sulfur bridges between CNTs and Co9S8 shows much better performance in terms of oxygen evolution (overpotential of 0.331 V at 10 mA cm−2) and oxygen reduction (half-wave potential of 0.810 V). Demonstrating that the sulfur bridges facilitate fast electron hopping from conductive support to active species, thus contributing to the outstanding electrochemical performance. Moreover, a rechargeable Zn-Air battery based on our electrocatalyst with strong sulfur bridges delivers an outstanding performance in terms of ORR and OER bifunctional performances. The clear understanding of the sulfur bridges between CNTs and Co9S8 is believed to shed substantial light on the development of other high-performance electrocatalysts.