Hollow structured N, S co-doped carbon nanotubes encapsulating Co/CoS2 nanoparticles as highly efficient electrocatalyst for Zinc-air battery

초록

The development of sustainable energy conversion and storage systems is crucial owing to the depletion of fossil fuels and energy crisis. Recently, rechargeable Zn-air batteries (ZABs) are regarded as promising energy devices due to their high specific energy density (1084 Wh kg), reliable safety and cost effectiveness. However, the ORR and OER involving a four-electron reaction process at cathode always suffer from sluggish kinetic behaviors during the charge and discharge process. Although noble metal-based materials (Pt/C for ORR and RuO2 for OER) are commonly used as the most excellent catalysts for ORR and OER, their high cost, monofunctionality and low electrochemical durability limit the practical application of ZABs. Consequently, it is essential to develop non-noble metal-based electrocatalysts with superior durability and high electrochemical activity for utilization of ZABs. Transition metal-based materials (alloys/ sulfides/oxides/ nitrides/ phosphides) have attracted considerable attention as electrocatalysts for rechargeable ZABs benefiting from their low cost, high electrochemical activity, and stable operation. Among the various candidates, transition metal sulfides have superior electrical conductivity compared with other chalcogenides, which is mainly attributed to the shallower valence band generated by S 3p orbital, resulting in formation of narrower band gap.