Preparation Of Iron-Cobalt Bimetal/Nitrogen-Sulfur Co-Doped Carbon Composites And Study Of Electrocatalytic Properties

Environmental pollution and resource depletion have become stumbling blocks to economic development and technological progress.Therefore,exploring and developing green and sustainable energy sources is crucial to the transformation of the energy structure.Due to their low cost,safety,environmental protection,and high conversion efficiency,electrolytic water devices and zinc-air batteries have emerged as popular research subjects in recent years.Both systems rely on electrochemical reactions like the oxygen precipitation reaction（OER）and oxygen reduction reaction（ORR）occurring at the electrodes to function,but their development is hampered by the reactions’high reaction potentials and slow chemical reaction rates.As a result,the creation of effective electrochemical reaction catalysts to lower the reaction’s activation energy and speed up the energy conversion rate becomes the key objective.Currently available precious metal catalysts,such as platinum and ruthenium dioxide,are capable of efficiently catalyzing oxygen reduction reactions and oxygen precipitation reactions,respectively.However,these catalysts’limited availability,high cost,and monofunctional catalytic properties prevent them from being used widely in industry.Since they are inexpensive,have access to a lot of resources,and have excellent catalytic activity,transition metal compounds have recently been recognized as a perfect alternative to noble metal materials.Based on the recent research status of transition metal OER/ORR catalysts and strategies to enhance catalytic performance and stability,this thesis proposes the design idea of bimetallic compound composite N,S co-doped porous carbon catalysts to prepare OER,OER/ORR bifunctional catalysts with excellent performance by constructing electrocatalysts rich in surface active sites to enhance energy conversion efficiency and will further applied to electrolytic water and zinc-air batteries.The research mainly includes:1.Bimetallic selenide（FeSe₂/CoSe₂）nanoparticles self-embedded in N,S co-doped carbon electrocatalysts（Fe Se₂/Co Se₂@NSC）were synthesized by in situ polymerization and low-temperature selenization strategies.The effects of Fe,Co co-doping,Fe/Co mono-doping,different metal ratios and selenide ratios on the catalytic performance were investigated for practical applications using solar-driven electrolytic water devices.Due to the synergistic effect of Fe Se₂and Co Se₂phases and the high conductivity and tunable electronic structure of N and S doped porous carbon,the Fe Se₂/Co Se₂@NSC catalyst has excellent OER catalytic activity and good durability in alkaline media,requiring only 278 m V overpotential to drive a current density of 10m A cm^-2,which is better than most metal selenide based catalysts reported in recent years chemical-based catalysts and commercial Ru O₂catalysts reported in recent years.2.Using silica as a template to aid pyrolysis,in situ production of Fe doped Co₉S₈nanoparticles embedded in honeycomb N,S co-doped carbon electrocatalysts（Fe/Co₉S₈@NSC）.Investigated were the effects of metal ratio and composition on catalytic performance.The experimental findings demonstrate that the Fe/Co₉S₈@NSC catalyst has an interconnected three-dimensional network structure and a sizable specific surface area to fully expose the numerous active sites,resulting in outstanding bifunctional capabilities of OER and ORR.With a current density of 10 m A cm^-2,the overpotential needed for catalytic OER can be as low as 332 m V,whereas the half-wave potential needed for catalytic ORR can be as high as 0.82 V.In addition,the Fe/Co₉S₈@NSC catalyst was further applied to Zn-Air battery devices,which showed high specific capacity(733 m Ah g^-1)and good charge/discharge stability,superior to that of Ru O₂+Pt/C catalyst.3.MOFs-derived Fe/Co bimetallic and nitrogen-sulfur co-doped carbon-based catalysts（e-Fe/Co@NSC-20）were prepared by a two-solvent method and high-temperature pyrolysis strategy.The effects of metal composition,Fe/Co metal ratio,and the core-shell structure material obtained by tannic acid etching on the catalytic performance were investigated and assembled into zinc-air cells for electrochemical performance evaluation.The e-Fe/Co@NSC-20 catalyst has excellent OER and ORR bifunctional properties due to its three-dimensional porous core-shell structure,high specific surface area to fully expose the active sites,and Fe doping induced charge transfer effect to optimize the adsorption of reaction intermediates.The overpotential needed by e-Fe/Co@NSC-20 to catalyze OER at a current density of 10 m A cm^-2was as low as 282 m V,whereas the half-wave potential needed for catalytic ORR was as high as 0.82 V.In addition,further application of the e-Fe/Co@NSC-20 catalyst to Zn-Air cells showed good multiplicative performance and high power density(136 mW cm^-2),which superior to RuO₂+Pt/C catalyst.