Design And Synthesis Of NiO-Based Catalysts And Electrocatalytic Performance For Oxygen Evolution Reaction

The energy of our country is mainly contributed by fossil fuels and is also faced the"poor oil","lean gas"and"rich coal"challenge.The comsumption of fossil fuels accounts for more than 80%of our country’s carbon emissions,causing severe environmental problems.In order to ahieve green and efficient development,we must adjust the energy comsumption structure and promote the energy revolution,that is,we must change the single dominant utilization of fossil fuels to integrate different types of energy sources working together,must optimize the utilization of fossil energy,and must promote large-scale renewable energy development.Given its high thermal conductivity,high energy density,and lack of environmental pollutants such as carbon monoxide（CO）and carbon dioxide（CO₂）when burned,hydrogen energy is regarded as one of the most promising fuels for the future.At the moment,the majority of existing hydrogen production technologies rely on fossil energy.Gray hydrogen produced by fossil fuel combustion and blue hydrogen produced by natural gas reforming by steam methane or self-heating steam reforming will inevitably generate greenhouse gases and other pollutants during the production process,whereas green hydrogen produces no carbon emissions during the production process thanks to renewable energy.As a result,finding an economical and efficient"decarbonization"method to produce hydrogen is a critical concern that is also the focus of global hydrogen energy development.It is regarded as one of the methods for producing green hydrogen now and in the future by using renewable energy to drive water decomposition.Electrocatalytic water decomposition includes cathode hydrogen evolution reaction（HER）and anode oxygen evolution reaction（OER）.Since the oxygen evolution reaction is a four-electron process,anode overpotential slows the the whole reaction process and causes electrical energy loss.At the moment,the main OER catalysts are Ir and Ru oxides,which are difficult to apply on a large scale due to their high price and limited reserves.It is critical to develop an anode catalyst with comparable performance.Because of its simple structure,adjustable electronic structure,and abundant reserves,nickel base oxide can improve its electrocatalytic activity by modifying strategies.Therefore,nickel oxide is chosen as the research model material in this thesis,with the detailed work mentioned below:Electrospinning was used to construct NiO materials with different amounts of Fe doping.Due to the radius difference between Fe and Ni ionic,Fe doped into part of the Ni lattice,resulting in a change in material lattice spacing.Transmission electron microscopy and element distribution were used to confirm the doping of Fe.The OER properties of Fe-doped Ni O series materials are researched.When the Fe content is 20%,the catalytic properties are optimal,and the overpotential is 360 m V at a current density of 10 m A/cm².It was discovered that Fe accelerated the reconstruction process by promoting the formation of OER active phase Ni OOH.Meanwhile,the lattice oxygen activity of the material did not change,and the AEM still dominated.Fe-doped Ni O materials with varying calcination temperatures were designed and synthesized in order to study the catalytic properties of OER in the presence of a magnetic field.The material transitions from a single Ni O phase to a mixed phase as the calcination temperature rises,and the Ni Fe₂O₄ phase appears after 700°C.When calcined at 500°C,the material exhibits excellent OER catalytic activity,with an overpotential of 362 m V at a current density of 10 m A/cm².Tafel slope,geometric area activity,mass activity,and electrochemical impedance test results all show that the material’s properties are superior to those of other calcination temperature and the comparison materials Ni O,Ni Fe₂O₄,and Fe₂O₃.The overpotential decreases by 25 m V under the influence of a200 m T magnetic field at a current density of 10 m A/cm²,showing that the material is more susceptible to magnetic field polarization and can significantly improve the catalytic activity of OER under the action of a magnetic field.Various loading capacities of La onto Ni O materials were designed and synthesized.Rare earth ions may not enter the Ni O lattice during the synthesis process due to their large radius.It is also demonstrated that La exists as oxide on the surface of Ni O using XRD,Raman,and transmission electron microscopy.The OER properties of La O_x/Ni O materials were evaluated under various loading.When the amount of La introduced was 2.5%,the material had the best OER catalytic properties,but long-term CV activation was required to obtain the optimal properties.The incorporation of La had no effect on the lattice oxygen activity of Ni O,and the AEM remained the dominant mechanism.In situ Raman tests revealed that La reduced the formation potential of Ni OOH while promoting the reconstruction process to enhance the material’s OER activity.