Preparation Of Co/N-Doped Hierarchical Porous Efficient Catalysts And Application To Zn-Air Batteries

In recent years,the focus of catalyst development has been on exploring alternative materials to traditional platinum-based catalysts,i.e.more efficient and durable catalysts.Among many non-noble metal catalysts developed,transition metal-nitrogen co-doped carbon catalysts（M-N/C,where M=Mn,Fe,Co,Ni,etc.）have become the most promising alternative to platinum-based catalysts due to their low cost,high electrical conductivity,good durability and adjustable active sites.Among them,cobalt-nitrogen co-doped carbon materials,due to their abundant cobalt reserves and high affinity for oxygen,have been widely studied as excellent dual-function catalysts.One of the most commonly used methods for constructing a Co-N/C catalyst is the direct thermal decomposition of a metal-coordinated carbon precursor and a nitrogen-containing compound mixture.In this study,a cobalt-nitrogen codoped hierarchically porous carbon dual-functional catalyst（Co/N-HPCs-800）was prepared using sustainable and earth-abundant sodium alginate（Na-Alg）as precursor to chelate excess metal ions.The morphology,structure and chemical composition of the material were investigated by scanning electron microscrope（SEM）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）and X-ray photoelectron spectroscopy XPS,respectively,which demonstrated that Co/N-HPCs-800possessed abundant hierarchical pores and highly loaded Co-N₄ active sites.Co/N-HPCs-800 exhibited excellent catalytic activity and durability in both oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）,with a high half-wave potential of 0.86 V in ORR and a low overpotential of 360 m V in OER.Importantly,the half-wave potential was only decreased by 8 m V after50 k cycles.Moreover,this dual-functional catalyst even performed better in alkaline media than most advanced commercial Pt/C catalysts and Ru O₂catalysts.In addition,zinc-air battery assembled by Co/N-HPCs-800 catalyst also showed remarkable performance and extremely high stability.This work opened up a practical and scalable new route for transition metal catalysts synthesized at extremely low cost,which could effectively improve the use performance of zinc-air battery to achieve higher efficiency and lower cost.