| To overcome serious ecology deterioration and energy shortages,rational development of efficient and sustainable energy conversion and storage technologies is highly crucial.Impressively,Zn-air batteries reveal significant prospect,thanks to their high energy density,environmental benignity,and low price.However,their wide implementations are severely limited via the sluggish kinetics of oxygen reduction reaction（ORR）and oxygen evolution reactions（OER）.So far,Pt/C and Ru O2/Ir O2 indicate as the most outstanding electrocatalysts toward ORR and OER,while scarcity and high cost of aforementioned catalysts severely hampers their practical applications.Consequently,it is urgent to design and synthesize low-cost and high efficiency bifunctional oxygen catalysts.In this paper,we synthesized three carbon-based composites electrocatalysts by facile one-step carbonization method.The morphology,structure and composition of as-synthesized product were characterized by a series of techniques.Furthermore,the electrocatalytic properties of these catalysts were carefully examined towards ORR,OER and Zn-air battery.The research contents are as follows:（1）Fe Co alloyed nanoparticles entrapped into the highly porous N-doped 3D honeycombed carbon:A high-efficiency bifunctional oxygen electrocatalyst for boosting rechargeable Zn-air batteriesHerein,Fe Co nanoparticles（NPs）embedded into N-doped honeycombed carbon（Fe Co@N-HC）was efficiently prepared by a one-step carbonization method in the existence of NH4Cl and citric acid.Benefiting from the honeycomb-like architectures and the synergistic effect of the Fe Co alloy with the carbon matrix,the as-synthesized Fe Co@N-HC exhibited outstanding ORR with the more positive onset potential(Eonset=0.98 V vs.RHE)and half-wave potential(E1/2=0.85 V vs.RHE),coupled with outstanding OER with the lower overpotential（318 m V）at 10 m A cm–2.Besides,the home-made Zn-air battery has the larger power density of 144 m W cm–2 than Pt/C+Ru O2(80 m W cm–2).This research offers some valuable guidelines for constructing robust oxygen electrocatalysts in clean energy storage and conversion technologies.（2）Mn,N,P-tridoped bamboo-like carbon nanotubes decorated with ultrafine Co2P/Fe Co nanoparticles as bifunctional oxygen electrocatalyst for long-term rechargeable Zn-air batteryHerein,fine Co2P/Fe Co NPs anchored on Mn,N,P-codoped bamboo-like carbon nanotubes（Co2P/Fe Co/Mn NP-BCNTs）are constructed in the coexistence of melamine,poly（4-vinylpyridine）and adenosine-5’-diphosphate disodium salt（ADP）by convenient pyrolysis and follow-up acid treatment.The as-prepared catalyst exhibits the higher Eonset（0.97 V vs.RHE）and E1/2（0.88 V vs.RHE）for ORR,coupled with excellent OER with the lower overpotential of 324 m V at 10 m A cm–2.Notably,the home-made Zn-air battery delivers the greater peak power density of 220m W cm–2,together with the outstanding cycling stability.This work offers a novel strategy to explore advanced bifunctional oxygen catalysts for high-efficiency metal-air batteries.（3）N,P-doped carbon nanotubes-on-nanosheets supported with Co Ni/Mo C nanoparticles:A synergy of 1D@2D heterostructure with multiple active sites for rechargeable Zn-air batteryHerein,N,P-doped carbon nanotubes-on-nanosheets supported with Co Ni/Mo C NPs（Co Ni/Mo C-NP-CTS）was prepared by simple one-step carbonization method.Benefiting from the composite structure of interconnected sheets/tubes,and the synergistic effect of metal nanoparticles and carbon support,the Co Ni/Mo C-NP-CTS shows improved ORR activity(E1/2 of 0.89 V vs.RHE and Tafel slope of 51.1 m V dec–1)and remarkable OER performance(overpotential of 335 m V at 10 m A cm–2).More notably,Co Ni/Mo C-NP-CTS-based Zn-air battery exhibits higher power density(132 m W cm–2)than commercial catalyst(80 m W cm–2)and outstanding cycling durability（480 cycles,160 h）.This work indicates an effective inspiration to design and construct considerable non-precious-metal electrocatalysts toward metal-air battery. |
