Doping Modulation And Synchrotron Radiation Characterization Of Water Splitting Electrocatalysts

The development of today's world has put forward new requirements for energy.Hydrogen energy has the advantages of clean and pollution-free,good combustion performance,and high utilization rate.It has important research significance and application value.Compared with other traditional technologies such as petroleum cracking,electrolysis of water is a common method for preparing hydrogen,and the whole process is environmentally friendly.In fact,the dissociation of water requires a very high energy barrier,and the use of catalysts can significantly reduce the reaction barrier and accelerate the reaction,so that the use of lower electrical energy can achieve the decomposition of water to produce hydrogen and oxygen.Among many electrolysis water catalysts,noble metals(such as Pt,Ir,etc.)exhibit excellent catalytic performance,but their high prices and limited resources hinder large-scale industrial applications.As a potential replacement,transition metal-based catalysts have gradually received widespread attention.At the same time,the application of synchrotron radiation characterization technology in the electrochemical field is becoming more and more extensive,especially the development of in-situ technology,which can analyze the electronic structure and coordination information of the catalyst in more detail from the atomic point of view,and promote the catalytic reaction process The mechanism needs to be deeply understood.Relying on the synchrotron radiation source,this thesis selects several electrolysis water catalysts as the research object,focusing on doping control,adopting strategies such as single metal doping,bimetal doping,metal and non-metal co-doping,combined with synchrotron radiation,etc.Characterization means,in-depth study of the effect of doping on the electronic structure and performance of the catalyst,reveals the synergy between different atoms,and provides a useful reference for the design of high-efficiency water electrolysis catalysts.The specific research results are as follows:1.Using CoP nanosheets as raw materials,a cobalt phosphide CoP material doped with W and Fe atoms is synthesized by hydrothermal method and used as a catalyst for total water dissolution.XRD,TEM and other characterization results found that W and Fe were only doped into the cobalt phosphide lattice in the form of atoms,and did not change the main phase of CoP.XPS test shows that the introduction of W and Fe doping effectively optimizes the electronic structure of CoP,so that electrons are transferred from Co atoms to P atoms.The comparative analysis before and after the complete water dissolution reaction shows that the W,Fe@CoP/CNTs catalyst supported on carbon nanotubes has undergone structural restructuring,and for the oxygen generation reaction,it will reconstitute Co-based oxides/hydroxides;The hydrogen production reaction will be reconstructed into the core-shell structure of phosphate-Co particles.Therefore,the co-doping of W and Fe can make CoP produce more defects,thereby speeding up the structural reconstruction in the catalytic reaction process,and finally forming efficient active sites.2.The graphene material with Ru single atom supported P and N co-doped was synthesized by high-temperature sintering method,and used as a hydrogen production catalyst for electrolysis of water.Theoretical calculation and XAFS characterization found that the co-introduction of Ru and P atoms into the N-doped graphene optimized its electronic structure and reaction kinetics,and formed a unique Ru-N4-P structure in the material.Electrochemical tests show that Ru atoms and P atoms play different roles respectively.The doping of Ru improves the conductivity of the catalyst,and the doping of P provides the catalyst with efficient hydrogen production catalytic sites.In-situ synchrotron radiation infrared spectroscopy shows that a P-Hads reaction intermediate will continue to be produced during the HER reaction,which is conducive to the rapid progress of electrocatalytic hydrogen production.3.The noble metal Ir-doped manganese dioxide MnO2 material was synthesized by a two-step hydrothermal and ion exchange method,and used as a neutral electrolytic water oxygen production catalyst.The test results show that Ir is inserted into the MnO2 layer in the form of atoms,which does not change the original main phase structure,but affects the electronic structure of the Mn atomic center,making the Mn atomic center gather more electrons and induce the formation of oxygen defect structure.This Ir doping effect brings more stable and high intrinsic catalytic activity active sites to MnO2,improves the utilization of precious metal Ir atoms,and also improves the oxygen production performance of MnO2 in a neutral environment.