Study On Mof Derived Transition Metals/N-doped Carbon Composites And Their Applications In Zn-air Battery

Advanced energy storage/conversion technologies and equipments are urgently needed to satisfy large-scale application of renewable energy and the rapid development of electric vehicles.Due to the advantages of environmental friendliness,high theoretical energy density and high safety,Zn-air battery have been widely used in medical treatment,portable electronic equipment,power grid storage and other fields,and are very promising batteries at present.However,due to the sluggish kinetics and limited stability in electrolytes of the oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）on the air cathode,their practical application is seriously hindered.At present,Pt and Ir O₂ precious materials have been acknowledged as the most advanced ORR and OER catalysts,respectively.However,the scarcity and poor stability greatly hinder its practical and large-scale application.Therefore,it is imperative to develop highly activity and durability bifunctional electrocatalysts as alternatives to noble-metal catalysts.Metal-organic framework materials（MOF）are a branch of porous crystalline materials constructed by organic ligands connecting metal ions/clusters.In view of the controllable composition,high specific surface area and enriched porous structure,MOF have broad application to prepare electrocatalysts.This paper will focuse on the different strategies for regulating the morphology and composition of MOF-derived carbon-based materials to achieve efficient electrocatalysts.The main contents and conclusions were summarized as follows:1.A multi-step approach to synthesize Co S,Co and Mo C nanoparticles modified in the N,S dual-doped porous carbon nanofibers bifunctional（Co S/Co/Mo C-N,S-PCNFs）catalyst for Zn-air battery.In this chapter,we have developed an efficient Co S/Co/Mo C-N,S-PCNFs bifunctional catalyst by multi-step approach involving polymerization,electrospinning,etching and high-temperature calcination.Benefiting from the advantages of the purposely designed 1 D nanofiber morphology,high surface area,nanoparticles incorporated in carbon nanofiber structure,and the integration of multiple active sites including Co S,Co and Mo C,the as-prepared Co S/Co/Mo C-N,S-PCNFs catalyst demonstrates excellent electrocatalytic performance toward the ORR and OER.High values of E₀（0.951 V）and E_1/2（0.871 V）have been achieved,which outperform those of commercial Pt/C catalyst.Moreover,Co S/Co/Mo C-N,S-PCNFs enables excellent activities including a high-power density(169.1 m W cm^-2),a large specific capacity(819.3 m A h g^-1)and a remarkable energy density(1008.1 W h kg^-1).Also,the as-assembled rechargeable Zn-air battery with Co S/Co/Mo C-N,S-PCNFs displays superior cycling stability than that based on Pt/C electrode.This work provides a simple and feasible strategy for preparation of efficient non-noble metal bifunctional electrocatalysts for energy storage.2.A facile design route with metal organic framework as the precursor to synthesis Co₃Fe₇and Co Fe₂O₄ nanoparticle Co-decorated N-doped carbon polyhedron（Co₃Fe₇-Co Fe₂O₄/NCPs）catalyst for Zn-air battery.In this chapter,we employed Fe-MIL-88NH₂ octahedrons as precursors to obtain desired electrocatalysts toward OER and ORR.In the special nanostructure,the homogeneous dispersion of Co₃Fe₇ and Co Fe₂O₄ in the porous nitrogen doped carbon polyhedron provides additional strong catalyst-support interaction to further enhance the catalytic activity and stability of the catalyst.Highly active Co₃Fe₇-NCNPs for ORR and Co Fe₂O₄/NCNPs for OER endows the sample with superior bifunctional electrocatalytic performance toward both OER and ORR,comparing with the state-of-the-art Pt/C catalysts.Moreover,the Co₃Fe₇-Co Fe₂O₄/NCPs-driven Zn-air battery can be stably charged and discharged cycling 130 h with high energy efficiency,outperforming the more costly Pt/C-driven Zn-air battery.This work provides a new efficient method for preparing durable,cost-effective and vastly active oxygen electrocatalysts.3.A facile strategy to synthesis of a new bifunctional electrocatalyst consisting of N-doped carbon hollow spheres（Co/Cu@NCHSs）co-decorated with Co and Cu nanoparticles catalyst for Zn-air battery.In this chapter,we demonstrated the synthesis of a superiorly active and durable bifunctional electrocatalyst made of copper（Cu）and cobalt（Co）nanoparticle co-decorated N-doped carbon hollow spheres.In special nanostructures,the presence of metal nitrides as highly effective active sites is beneficial to improve the electrocatalytic activity.The results show that Co/Cu@NCHSs exhibits excellent ORR and OER performance.In the liquid Zn-air battery,it gives rise to the high voltage of 1.51 V and the maximum power density of 226 m W cm^-2.It is worth noting that the liquid Zn-air battery can stable charge and discharge for 1000 h.The present study provides a new avenue for the exploration of non-noble metal-based electrocatalysts by the synergy of metal nanoparticles assembled in a conducting substrate such as carbon-based materials.In order to improve the activity and stability of the catalysts,non-noble metal catalysts were prepared by different synthesis methods with different MOF as precursors.Using scientific characterization,the influence of different components on the catalytic activity was systematically explored.The synthesized catalyst has the advantages of low cost,simple synthesis and excellent performance,which is of great significance for the realization of precise control and mass production of high efficiency electrocatalyst.