Design And Synthesis Of Fe-based Metal Organic-derived Materials And Their Electrochemical Properties

Electrocatalysis technology is widely used in the fields of clean energy and environmental protection,especially in the areas of clean and efficient sustainable energy utilization and green organic synthesis.For example,electrolysis technology is used to produce high-purity oxygen and hydrogen,alcohol electrocatalytic oxidation in fuel cells,and electrochemical oxidation.The key to these technologies is the development and application of efficient electrocatalysts.However,currently,commercial catalysts are mainly based on precious metal-based catalysts such as Pt,Ir,Ru,and others,which severely limit their application due to their scarcity,high cost,and poor resistance to poisoning.Therefore,developing electrocatalysts with high stability,low cost,and high activity is of great significance to promote the development of the aforementioned fields.Metal-organic gel materials（MOGs）are a new type of functional material mainly formed by self-assembly of metal ions and organic ligands through coordination bonds,hydrogen bonds,π-πstacking,van der Waals forces,and other non-covalent interactions,with a large specific surface area,adjustable structure,and rich metal sites,with potential applications in adsorption,sensing,and catalysis.The research group’s previous exploration found that MOGs used as electrocatalytic water decomposition materials can exhibit good electrocatalytic performance,but under strong alkaline electric conditions,the MOGs’structure is difficult to maintain,often leading to reconstruction reactions.Based on the previous work of the research group,this paper focuses on the design and synthesis of iron-based metal-organic gel materials and their derivative materials’electrocatalytic performance,obtaining some regular conclusions,providing valuable reference for further research on such electrocatalytic materials.The specific content is as follows.:Part Ⅰ:Firstly,an overview of the research progress in the field of electrocatalytic hydrogen production is presented.Secondly,the synthesis and application of metal-organic gel materials and their derivative materials are discussed.Finally,the rationale and research content of this paper are introduced.Part Ⅱ:The reagents and instruments used in this paper,as well as the testing techniques for physical and chemical characterization and performance research,are introduced.Part Ⅲ:Fe Ni bimetallic metal-organic gel（Fe Ni-MOG）was successfully synthesized using a solvothermal method.Subsequently,Ni OOH/Fe OOH heterostructured materials were prepared through electrochemical reconstruction.While characterizing the physical and chemical properties,including phase structure,morphology,and basic properties of the heterostructured materials,the electrocatalytic oxygen evolution reaction（OER）performance was particularly explored.Due to the synergistic effect between the bimetallic centers and the rich hetero-interface between Ni OOH and Fe OOH,the heterostructured material showed excellent OER performance:at a current density of 10 m A cm^-2,the overpotential was 220 m V and the Tafel slope was 48 m V dec^-1,which is superior to most reported electrocatalytic OER materials in recent literature.Part Ⅳ:A three-element sulfide composite material with sulfur vacancies was synthesized using the in-situ sulfidation of a metal-organic gel of iron series elements via a hydrothermal method.A short and efficient Ar plasma treatment process was used to regulate the amount of sulfur vacancies on the surface of the material by varying the processing power,and the influence of different sulfur vacancy concentrations on the electrocatalytic oxygen evolution reaction（OER）performance of the material was investigated.The constructed multi-metal sulfide（Fe Co Ni S_x）material,benefiting from the multi-component heterojunction interface structure and appropriate sulfur vacancy modification,exposed more catalytic active sites to promote the catalytic activity of the material.Among them,when the power was treated at 400W,the material showed the best OER performance.In a 1.0 M KOH electrolyte,at a current density of 10 m A cm^-2,the overpotential was 235 m V,the Tafel slope was only 31 m V dec^-1,and the stability could be maintained for 11 hours at this current density.Part Ⅴ:A bimetallic metal-based organogel material with trace noble metal loading was grown in situ on the surface of nickel foam using a solvothermal reaction,followed by vapor phase phosphorylation to obtain transition metal phosphide composites（noble metal-Fe Co P/NF）,and the effects of different noble metal types and doping amounts on the electrocatalytic decomposition of water performance of the material were explored,as well as the general applicability of the method to a variety of noble metal doping.The oxygen precipitation（OER）performance and hydrogen precipitation（HER）performance of the materials were tested in an electrolyte of 1.0 M KOH.The tests showed that the electrochemical performance of the materials was enhanced regardless of the type of noble metal doping,and the overpotential of the materials in the OER test was in the following order for a current density of 50 m A cm^-2:Ru-Fe Co P/NF（192 m V）,Au-Fe Co P/NF（271 m V）,Pt-Fe Co P/NF（345 m V）,and Pd-Fe Co P/NF（200 m V）;in HER test,the overpotentials of the materials at a current density of 10 m A cm^-2 were in the following order:Ru-Fe Co P/NF（39 m V）,Au-Fe Co P/NF（176 m V）,Pt-Fe Co P/NF（93 m V）,and Pd-Fe Co P/NF（98 m V）.Among them,Ru-Fe Co P/NF is a highly efficient bifunctional electrocatalyst,which was assembled as both cathode and anode in a fully electrolytic water device with a cell voltage of 1.64 V at a current density of 50 m A cm^-2,which is superior to most of the bifunctional electrolytic water catalysts reported in the literature.Part Ⅵ:Summary and outlook of the work in this thesis.