Preparation And Properties Of MOF Derived Textile Based Electrode Materials For Zinc-Air Batteries

As the progresses in social development and the standard of living becoming more advanced,human’s demand for green energy becomes more and more intense,so it is of great significance to develop sustainable energy storage and conversion devices.Zinc-air battery（ZAB）is considered as one of the most promising green energy storage and conversion devices due to its advantages of relatively high energy density,low cost,safety and no pollution.However,the mechanism of oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）involved in the cathode of zinc air battery is complex and the overpotential is high,which greatly limits the application of ZAB.At present,Pt/C,Ir O₂and Ru O₂ are considered to be the most excellent ORR and OER catalysts,but they cannot be widely used due to their high cost,scarcity and poor long-term stability.Therefore,the development of non-noble metal catalysts with high activity,high stability and low cost has considerable practical significance to promote the commercialization of ZAB.Metal-organic framework material（MOF）is a kind of polymer developed rapidly in recent years.It usually uses metal ions as connection points and organic ligands as support to form three-dimensional structure.Besides zeolite and carbon nanotubes,MOF is a new kind of porous material,which is widely used in catalysis,energy storage,separation and other fields.In addition,derivative materials prepared with MOF as a precursor system are also widely used in clean energy storage and conversion systems.In this paper,MOF was used as precursor to construct one-dimensional porous tubular carbon nanofiber single-function electrode materials and three-dimensional layered flexible integrated dual-function electrode materials by introducing different dimensions of substrate（fiber,fabric）for structural regulation,and to explore their catalytic performance in liquid zinc air batteries and flexible solid zinc air batteries.A one-dimensional porous carbon nanofiber（Co@Fe-CNFs）was prepared by carbonization,electrodeposition and recarbonization of electrospun nanofibers（Zn Fe-MOF/PAN）.By controlling electrodeposition time and carbonization temperature,Co@Fe-CNFs-1000 catalyst with good catalytic activity and stability was prepared.Co@Fe-CNFs-1000 is a hollow structure with a small number of carbon nanotubes on the surface of the fiber.A large number of Co nanoparticles are evenly dispersed and wrapped in carbon matrix,which can not only realize efficient and rapid electron transfer,but also prevent the oxidation and aggregation of Co nanoparticles.In addition,the synergism of Co-N_XC and Fe-N_XC active sites is added.Thus,the electrocatalytic activity and durability are improved.In addition,the large specific surface area,porous structure and interconnected three-dimensional carbon networks also play an important role in improving electrocatalytic performance.The Co@Fe-CNFs-1000 catalyst showed excellent ORR catalytic activity（half wave potential of 0.81 V）,comparable to that of industrial Pt/C catalysts（half wave potential of 0.81 V）.The liquid ZAB assembled with Co@Fe-CNFs-1000 as the air cathode has an open-circuit voltage of 1.48 V,a peak power density of 155.8 m W cm^-2,and long cycle stability that can last up to 100 hours at 2 m A cm^-2.The flexible all-solid ZAB with Co@Fe-CNFs-1000 as the cathode catalyst also exhibits excellent flexibility and bendability.Also developed is a dual-function self-supporting electrocatalyst CC/Co@NC/Co Fe-LDH-700 with high efficiency,low cost and long life.The layered bihydride（Co Fe-LDH）nanosheets were strongly coupled to the surface of a carbon cloth（CC）supported phylloidal bimetallic MOF derived hybrid carbon（Co@NC）nanoarray by liquid deposition,high temperature calcination and electrodeposition.The interfacial engineering of Co Fe-LDH coated on Co@NC improves the electronic conductivity of Co Fe-LDH nanosheets and achieves the balance of oxygen evolution reaction（OER）and oxygen reduction reaction（ORR）activities.The unique three-dimensional（3D）open interconnected layered structure facilitates the transport of substances during electrochemical processes while ensuring full exposure of OER/ORR active centers.CC/Co@NC/Co Fe-LDH-700 can be used as binderless air cathode for liquid ZAB with open circuit potential of 1.47 V,maximum power density of 129.3 m W cm^-2 and specific capacity of 710.7 m Ah g_Zn^-1.In addition,the flexible all-solid ZAB assembled from CC/Co@NC/Co Fe-LDH-700 demonstrated satisfactory mechanical flexibility and stable cycling performance within 40 hours.This work provides a new idea for the design of high performance self-supporting non-noble metal bi-functional electrocatalysts and ZAB air cathodes.