Preparation And Properties Of Doped Carbon Coupled Oxygen Electrode Materials

Among many energy storage and conversion technologies,metal-air batteries have shown great application potential due to their own advantages,and zinc-air batteries,as a very important category,have become the current research hotspot and have very considerable application prospects.However,due to the slow oxygen electrode reaction kinetics and mass transfer kinetics of zinc-air batteries,and poor stability,the potential advantages of zinc-air batteries are difficult to fully utilize,and the preparation of oxygen electrode materials is a technical problem.Therefore,the development of high-performance oxygen electrodes is essential to improve the performance of zinc-air batteries（energy density,rate performance,cycle stability,etc.）.Carbon materials have the advantages of high specific surface area,high conductivity,adjustable structure,convenient preparation,economical feasibility,etc.,and have been widely reported in the field of electrocatalysis.However,a single carbon material has certain limitations in practical applications,and nano-carbon materials can be combined with various organic and inorganic materials to prepare catalysts with excellent performance to achieve the effect of replacing precious metal catalysts.Therefore,by reasonably coupling different active components with carbon-based materials,ideal doped carbon-based coupled oxygen electrode materials can be prepared.In this thesis,a series of low-cost and high catalytic activity oxygen electrode catalytic materials were prepared by using poly-m-phenylenediamine and zeolite imidazole framework nitrogen-doped carbon precursors,respectively,after compounding with YF₃,Co S₂and Ni Co₂O₄.First,a series of YF₃@NC composite catalytic materials were prepared by coating spherical YF₃with poly-m-phenylenediamine and pyrolyzed.The ORR catalytic performance and its application as an oxygen electrode in zinc-air batteries were studied.Second,eutectic salt was used as template,pyrolyze the iron-containing poly-m-phenylene diamine to obtain porous Fe NC,and load Co S₂on the surface to realize the coupling of Fe NC and Co S₂to obtain Fe NC-Co S₂coupling hybrid material.The bifunctional catalytic performance of Fe NC-Co S₂was studied.The application as an oxygen electrode in a zinc-air battery is investigated;third,a ZIF-derived doped carbon material is coupled with Ni Co₂O₄to achieve dual-functional catalysis,and it is used as an oxygen electrode material in a wearable zinc-air battery.In addition,SEM,TEM,XRD,XPS,BET,Raman and other tests were used to characterize the catalyst structure.The specific results are as follows:Part I:Nitrogen-containing carbon doped with yttrium fluoride as a high-efficiency oxygen electrode catalyst for zinc-air batteriesUsing m-phenylenediamine as nitrogen and carbon source,a YF₃doped nitrogen-containing carbon（YF₃@NC）electrocatalyst was prepared.Yttrium chloride,ammonium fluoride and L-arginine are used as Y source,F source and auxiliary agent,respectively.The YF₃spherical precursor is obtained by a simple arginine-assisted hydrothermal method,and then the spherical YF₃is coated and pyrolyzed at high temperature to prepare YF₃@NC.It has a positive starting potential（0.943 V）,half-wave potential（0.836 V）,high current density and good cycle stability（10 hours degradation:13%）.When YF₃@NC is used as a zinc-air battery oxygen electrode catalyst,the resulting battery has a high open circuit potential（1.478 V）and peak power density(75 m W cm^-2).PartⅡ:Strong coupling of Co S₂and porous Fe NC as a high-efficiency bifunction catalyst for rechargeable zinc-air batteriesUsing eutectic salt assisted semi-closed carbonization strategy,three-dimensional porous KCl+Zn Cl₂eutectic salt was prepared by freeze-drying method.Then,polym-phenylene diamine（Pm PD）was polymerized on the surface of the three-dimensional porous KCl+Zn Cl₂eutectic salt.Then,the obtained solid is thermally decomposed and acid leached to obtain a three-dimensional porous structure.Finally,through simple hydrothermal and vulcanization steps,Co S₂was grown on the porous Fe NC.Fe NC-Co S₂catalyst shows good electron and mass transfer capabilities,exposing a large number of ORR/OER active sites.Therefore,it exhibits excellent catalytic activity and durability(E_1/2=0.848 V)and OER(E^-2_{j=10 m A cm}=1.608 V).In addition,the assembled rechargeable zinc-air battery showed excellent discharge peak power density～117.6 m W cm^-2and high capacity of 581.3 m Ah g _Zn^-1,as well as excellent reversibility and stability.Part III:ZIF-derived doped carbon materials coupled with Ni Co₂O₄as oxygen electrode materials used in wearable zinc-air batteriesA two-dimensional Co,N-doped carbon nanosheet（Co NCNS）was generated by pyrolyzing the leaf-shaped ZIF,and then a coupled hybrid bifunctional electrocatalyst（Ni Co₂O₄/Co NCNS）was obtained by hybridization with Ni Co₂O₄by hydrothermal method.It exhibits excellent bifunctional catalytic activity ORR(E_1/2=0.849 V)and OER(E^-2_{j=10 m A cm}=1.582 V).In addition,using Ni Co₂O₄/Co NCNS as the zinc air oxygen electrode catalyst,the assembled zinc air battery exhibits high power density(148.3 m W cm^-2),high specific capacity(699.9 m Ah g _Zn^-1).After 115 hours of charge and discharge the cycle still shows excellent stability and reversibility.The experimental results show that the three doped carbon-based coupled oxygen electrode materials have the characteristics of stable structure and excellent catalytic performance.As the oxygen electrode of zinc-air battery,they can effectively make up for the disadvantages of zinc-air battery’s poor rate performance and low cycle life.It shows that doped carbon-based coupling materials have great application potential in the application of oxygen electrodes in zinc-air batteries.