Effects And Mechanism Of La_xSr_1-xCr_yNi_1-yO₃ Powders’ Exsolution Characteristics Under Pulsed Current

Exsolution-type perovskites have a wide range of applications in solid oxide fuel cells,automotive exhaust gas treatment and other fields,because of its excellent electrochemical interface can improve the electrocatalytic activity.At present,there are few means to promote the exsolution of perovskites,including high-temperature hydrogen reduction,voltage application,and acid etching.In this paper,pulsed current（PC）treatment technology was introduced into perovskite exsolution treatment.La_xSr_1-xCr_yNi_1-yO₃ powders were prepared by sol-gel method.The exsolution properties of powders under PC were studied.The distribution ratio has a certain influence on the crystallization performance of La_xSr_1-xCr_yNi_1-yO₃ powders.The experimental results show that when the La/Sr ratio of La_xSr_1-xCr_yNi_1-yO₃ powder is 0.85:0.15,the La_xSr_1-xCr_yNi_1-yO₃ powders with different distribution ratios of Cr and Ni are various in the structure the morphology.At the same calcination temperature and calcination time,the doping content of Ni element decreases,and the crystallization performance correspondily increases.Under the action of PC,the prepared Ni doping elements of La_0.85Sr_0.15Cr_0.9Ni_0.1O₃powders are in situ exsoluted.The exsolution peaks of Ni element have been found on the XRD spectra,and the SEM images of the exsolution particles are observed with different numbers and sizes.After the PC treatment,the electrochemical performance of the powder was improved,and the impedance value was reduced from the real part of 350?/cm²,the imaginary part of 800?/cm² to the real part of 6?/cm²,and the imaginary part of about20?/cm².With the increase of pulse voltage,the cyclic voltammetry characteristics of La_0.85Sr_0.15Cr_0.9Ni_0.1O₃ powders are obviously improved.The change of the pulse frequency mainly affects the electrochemical impedance characteristics of the powder.When the pulse voltage and frequency are given,the PC treatment time increases,and the electrochemical cycle characteristics and impedance of the powder are improved.It is considered that PC treatment forms a large instantaneous current inside the La_0.85Sr_0.15Cr_0.9Ni_0.1O₃ powder,accompanied by a large amount of Joule heat.The injection of charge reduces the Ni element from the ionic state and exsolution the bulk phase from the perovskite body.The exsolution preparation method of perovskites proposed is expected to provide a novel idea for the improvement of the performance of solid anode oxidation for fuel cell anode materials.