The Construction And Application Of Fe-based Nitrides And Phosphides For Rechargeable Zinc-Air Batteries

At present,the protection of the environment and the building of a sustainable energy system on a global scale are the most critical challenges for humanity.With the advancement of technology and society,finding new energy conversion and storage systems and developing low-cost,high-efficiency energy technologies have become important topics.Compared with lithium-ion batteries which are widely used in portable devices,rechargeable zinc-air batteries(ZABs)have received more and more attention due to their high theoretical energy density(1086 Wh kg-1),good safety,and environmental friendliness.However,the following problems still exist:the sluggish kinetics of oxygen reduction reaction(ORR)and oxygen evolution reactions(OER)on the air cathode lead to low power density,low charge-discharge efficiency,and poor long-term cycling performance of the batteries.To address these issues,this thesis focuses on the design of novel bifunctional catalytic materials,using iron-based nitride and phosphide as the research targets.Meanwhile,this thesis also conducts a systematic study in terms of the synthesis and performance improvement of catalysts.The specific research contents of this thesis are as follows:(1)Firstly,the Fe2O3/NiO precursors were prepared by a simple hydrothermal method using aqueous solutions of iron nitrate nonahydrate and nickel nitrate hexahydrate.Then the Fe0.64Ni0.36@N-CNTs was fabricated by a concurrent-thermal decomposition method using dicyandiamide as the raw material.Finally,the Fe0.64Ni0.36/Fe2Ni2N@N-CNTs composites were synthesized by nitriding process.The domain-limiting effect of hollow bamboo-like carbon nanotubes ensures the good dispersion of Fe0.64Ni0.36/Fe2Ni2N nanoparticles and alleviates the corrosion of the metals by the electrolyte.Furthermore,the heterogeneous structure of the alloy and nitride modulates the electronic structure and increases the number of active sites,and the abundant mesopores ensure sufficient infiltration of the electrolyte.Owing to the unique structural features,the materials exhibit superior bifunctional catalytic activity(ΔE=0.73 V).The liquid zinc-air batteries possess a high power density(137 mW cm-2)and long cycle life(380 h,5 mA cm-2,and 280 h,10 mA cm-2).Flexible zinc-air batteries also have good cycling stability(20 h,2 mA cm-2).(2)A series of transition metal phosphides with hollow,"wall-sharing" structures have been synthesized using a general "in situ etch-adsorption-phosphatization" strategy.The ZIF-8 is used as the sacrificial template.Phytic acid is also acted as the phosphorus source and etching agent.Considering Fe(heme)and Cu(copper terminal oxidases)are nature’s options for oxygen reduction reaction(ORR)catalysts in many forms of life from bacteria to humans.Fe-P/Cu3PNPC has the best bifunctional catalytic performance(ΔE=0.74 V)for the ORR and OER.The liquid zinc-air batteries with Fe-P/Cu3P-NPC as cathode exhibit a high peak power density of 158.5 mW cm-2 and excellent long-term cycling performance(～1100 cycles at 2 mA cm-2).Similarly,the flexible ZABs deliver superior cycling stability of 81 h at 2 mA cm-2 without bending.This work paves a novel approach to enhance the bifunctional catalytic activity of Febased TMPs.