Effect Of Structure Regulation On Pulsed Current Induced Perovskite Exsolution And Its Mechanism

In recent years,the exsolution-type metal nanoparticle oxide has been widely used as a promising catalyst.There is a relatively stronger interaction between the metal particles of the exsolution type catalyst and the oxide matrix,which helps the transmission of electron ions at the metal-oxide interface.The B-site exsolution of perovskite induced by pulse current has the characteristics of high efficiency,no pollution,simple operation and effective reduction of reaction time,which can break through the limitations of the high temperature reduction method and is expected to become a new technology for controlling the exsolution of perovskite.Systematic control of the structural composition of the perovskite-type oxide matrix and external conditions,including changing the preparation process,element doping and pulse current parameters,and discuss the influence of different structures on the exsolution behavior of perovskite B-site induced by pulse current.The influence of the structure and morphology on the pulse current treatment of perovskite-type oxide powder was studied by changing different preparation processes.The results show that the sample prepared by the sol-gel method has a cubic structure and can induce the exsolution of the B-site transition metal Ni element after pulse treatment.The size of the exsolved particles is between 20～60nm.After the exsolution,the matrix structure remains unchanged and has no other miscellaneous phases;The samples prepared by the solid-phase reaction method did not find element precipitation after applying pulse current,and the matrix was a solid solution in which cubic and orthorhombic crystals coexist,and the matrix bonding bond was tight and it was not easy to exsolved.Electrochemical tests show that after pulse current treatment,the electrocatalytic performance of the materials has been greatly improved.The introduction of vacancies at the A-site has a different effect on the exsolution behavior of the perovskite B site induced by pulse current.The results show that when the A-site is not doped or doped in stoichiometric ratio,the prepared sample is accompanied by the generation of NiTi,SrO and Ti₃O₅ impurities,and some of the impurity diffraction peaks disappear after the pulse current is applied.Smaller,electrochemical test results show that after pulse current treatment,the CV,LSV and EIS performance of the material can be improved;when the A-site is doped with 52at%La,the pulse treatment can inhibit the formation of intermetallic compounds.At the same time,the exsolution of Ni nanoparticles was observed.After the pulse current treatment,the charge transfer resistance R_ct value was reduced to 2.153Ω·cm²,which can accelerate the charge transfer and make it have better electrocatalytic activity.In order to further explore the impact of constructing a new perovskite-type oxide interface structure based on pulse current technology on the exsolution behavior of perovskite,La_0.52Sr_0.28Ti_0.9Ni_0.1O₃ was used as the research object,adjust and control pulse parameters（voltage,time）.When the pulse voltage is 500V,a clearer characteristic diffraction peak of Ni phase and no other impurity phases are observed.When the pulse voltage is increased to700V,apart from the precipitation of Ni elemental substance,LaNi nano-alloys are also observed;The treatment time affects the exsolution behavior of the B-site also has a certain effect.The processing time of 60s can obtain Ni nanoparticles that are uniformly distributed on the surface of the material.The electrochemical test results show that the electrocatalytic activity of the material is improved after the pulse current is applied.When the pulse parameter is 500V-3Hz-60s,the initial oxygen evolution potential of the sample is the most negative（≈0.505V,vs.SCE）,and the peak current can reach 266.7m A/cm²,showing excellent electrocatalytic performance.This research opens up a new perspective to design the relationship between surface interface and defect,particle and matrix interface,which will be of great significance to the study of high-activity,low-cost perovskite-type catalysts and in various energy conversion systems application potential.