Preparation Of Transition Metal Catalysts For Phosphorus And Sulfur Compounds And Study On Electrocatalytic Oxygen Evolution

Due to the excessive development of non-renewable resources and the increasing environmental pollution,researchers are actively exploring and developing renewable energy.Hydrogen energy as a high energy density,zero pollution and a wide range of sources of clean sustainable energy,its large-scale development is only the way for our country to realize carbon peak and carbon neutralization strategic vision on high-quality schedule.Electrochemical water splitting hydrogen production technology is considered as one of the most promising hydrogen production technologies because of its advantages of high purity,no pollution and simple operation.However,anodic oxygen evolution reaction involving a multi-electron transfer process is kinetic slowly,which severely limits the energy conversion efficiency in the whole process.At present,Ir O₂and Ru O₂show high catalytic activity for oxygen evolution,but their wide application is limited by the shortage and high cost of noble metal materials.Therefore,the development of low cost and high efficiency transition metal oxygen evolution catalyst is of great significance for promoting the commercialization of hydrogen production technology by water splitting.In this paper,layered bimetallic hydroxide（LDH）and its derived phosphide,metal-organic frame material（MOF）and its derived phosphide and sulfide are the main research objects,and explore their oxygen evolution reaction performance and reaction mechanism,the main research content is as follows:1.Design and electrocatalytic performance of phosphide catalysts derived from LDH（1）The precursors of NiFe-LDH and NiFe-LDH@CNT were synthesized by hydrothermal method,and the catalysts NiFe P and Ni P₂/Fe P@CNT were obtained by further phosphating.The experimental results indicate that compared with NiFe-LDH,NiFe-LDH@CNT and NiFe P,Ni P₂/Fe P@CNT showed excellent electrochemical performance,even exceeding that of the commercial material Ru O₂.When the current density is 10 m A cm^-2,the target catalyst requires only 261 m V overpotential,the Tafel slope is 44 m V dec^-1,and the current density does not decrease significantly during the 20 h i-t test.These excellent electrochemical properties are mainly attributed to the unique morphology of the catalyst,the synergistic interaction between heterogeneous phases,and the addition of carbon nanotubes.（2）The precursors of CoFe-LDH and CoFe-LDH@CNT were prepared by similar method,and CoFe P and Co P/Fe P₄@CNT were obtained by phosphating,respectively.The morphology of the precursor CoFe-LDH@CNT is solid nanorods,while that of Co P/Fe P₄@CNT is hollow.This significant change increases the active surface area of Co P/Fe P₄@CNT,which is conducive to exposing more reactive sites.The results indicate that the electrocatalytic activity of Co P/Fe P₄@CNT is indeed better than that of CoFe-LDH@CNT,because Co P/Fe P₄@CNT requires only 301 m V overpotential at 10 m A cm^-2current density,and the Tafel slope is 48 m V dec^-1,the latter requires an overpotential of 355 m V.However,the onset potential of Co P/Fe P₄@CNT is slightly higher than that of commercial Ru O₂.Fortunately,as the current density gradually increases,the performance of Co P/Fe P₄@CNT gradually exceeds that of the latter,which indicates that Co P/Fe P₄@CNT has good kinetic performance.In conclusion,the excellent electrochemical performance is mainly related to the unique morphology of hollow nanorods and the construction of heterogeneous interfaces.2.Design and electrocatalytic performance of MOF derived phosphide catalystsA series of catalysts for Fe-doped Ni P₂/Ni₂P composite carbon nanotubes containing different Ni/Fe ratios were prepared by hydrothermal method and phosphating process.The results show that the catalyst Fe-（Ni P₂/Ni₂P）@CNT-2 exhibits excellent electrochemical performance when the nickel-iron ratio is 3:1.The overpotential and Tafel slope corresponding to the current density of 10 m A cm^-2are 254m V and 46.1 m V dec^-1,respectively.Iron doping not only optimizes the electronic structure around Ni atoms,but also produces lattice distortions and lattice fringe defects,thus exposes considerable active sites.3.Design and electrocatalytic performance of MOF derived sulfide catalystsHeterogeneous FeNi₂S₄/Ni₃S₄@CNT catalyst was directly synthesized by one-step solvothermal method and its OER properties were investigated.The results show that FeNi₂S₄/Ni₃S₄@CNT has excellent catalytic activity,which is significantly better than all the catalysts in the control group.FeNi₂S₄/Ni₃S₄@CNT requires only 247m V at 10 m A cm^-2current density,and the Tafel slope is 53.7 m V dec^-1.When the morphology of the catalyst was characterized,it was found that the carbon nanotubes could pass through the nanoparticles,which fully guaranteed the internal conductivity of the nanoparticles.In addition,the powerful synergistic effect between the two nanoparticles can reduce the energy barrier and accelerate the oxygen evolution reaction.