TrimetallicPBA-derived FeCo/Fe-Co-S heterostructure embedded in N, S-doped carbon spheres as an efficient bifunctional electrocatalyst for Zn-air batteries

초록

The increasing demand for environmental pollution and the depletion of fossil fuels have made it urgent to develop green and sustainable energy conversion and storage systems. Due to high specific energy density, cost-effectiveness, and lightness, rechargeable metal-air batteries are considered as promising energy systems. Among them, rechargeable zinc-air batteries (ZABs) have attracted great attention owing to abundance, low-cost, and high safety. Oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) occur during the charging and discharging processes for ZABs. Despite these advantages of ZABs, both reactions involving four electrons have the sluggish kinetics, thus obstructing extensive application of ZABs. To date, precious metal-based electrocatalysts including Pt/C and RuO2 have been widely used for OER and ORR. However, their high cost, scarcity, poor durability, and limited bifunctionality pose serious problems for the widespread commercialization of ZABs. Therefore, it is important to develop the efficient transition metal-based electrocatalysts for rechargeable ZABs. For many years, extensive efforts have been devoted to the development of the transition metal-based materials (e.g., transition metal alloys, sulfides, oxides, and phosphides). Among them, transition metal sulfides (TMSs) have emerged as possible alternatives on account of numerous active sites, reversible redox properties, and narrower bandgaps than transition metal oxides. Despite relatively narrow bandgap, the electrochemical performance can be improved by further using the transition metal alloys (TMAs). The heterointerfaces between TMAs and TMSs modify the electronic structure, optimize the ad/desorption of reaction intermediates, and expose more active sites. Furthermore, introduction of sulfur vacancy into TMS provides a lot of lone-pair electrons and forms fast electron transfer channels, therefore getting better intrinsic activity toward oxygen-associated reaction.