Preparation And Characterization Of Doping La₂Ce₂O₇ Electrolyte For Intermediate Temperature Solid Oxide Fuel Cells

Solid oxide fuel cells(SOFCs)are devices to convert chemical energy of fuel directly into electrical energy,which has been more and more concerned by researchers because of the advantages of simple structure,high conversion efficiency,no pollution,no noise and the convenient of using.The high operating temperature is an important factor of limiting the commercialization of SOFCs for current technology.Therefore,reducing the operating temperature of SOFCs can improve the stability and service life of SOFCs,reducing the manufacturing cost,which will further promote the commercialization of SOFCs.It requires a sufficiently high conductivity of the electrolyte at low temperatures to ensure good electrochemical performance of SOFCs.The use of proton ceramic as SOFCs electrolyte material is one of the effective ways to reduce the operating temperature of SOFCs.In this study,a novel proton-conducting electrolyte material of doping La2Ce2O7 is prepared and the conductivity and electrochemical performance of doping La2Ce2O7 are studied.The results of Na doped La2Ce2O7(0?<x?0.20)show that La2-xNaxCe2O7-? powders are single phase fluorite structure by sol-gel method.The grain size of the La2-xNaxCe2O7-?electrolyte increases with the increase of the doped Na content after sintering at 1500 ?for 5 h,and the electrolyte grain size first increases and then decreases.The grain size reaches maximum value when the Na doping amount x=0.15 mol.The increase of grain size can effectively reduce the number of grain boundaries and increase the conductivity of La2-xNaxCe2O7-?.When the Na doping amount x = 0.15 mol,the conductivity of La1.85Na0.15Ce2O7-6 reaches a maximum value of 1.38 × 10-2 S/cm at 700 ? in 5%HZ-95%Ar atmosphere.At the same time,the peak power density of the single cell prepared with La1.85Na0.15Ce2O7-? electrolyte is 0.501 W/cm2 with 0.933 V open cell voltage at 700 ?.The surface oxygen vacancies and conductivity of Mo doped La2Ce2O7(O?x?0.20)are studied.The Raman and photoelectron spectroscopy test results show that proper Mo doping can effectively increase the oxygen vacancies of La2-xMoxCe2O7+? surface,increasing the electrical conductivity finally.The conductivity of La1.85Mo0.15Ce2O7+s is 1.65 × 10-2 S/cm at 700 ? in 5%H2-95%Ar atmosphere when the Mo doping amount x=0.15 mol,which is 96.4%higher than that of La2Ce2O7 electrolyte at the temperature of 700 ?.The maximum power density of the single cell prepared with La1.85Mo0.15Ce2O7+?electrolyte is 0.643 W/cm2 at 700 ?,reaching good performance.The application of La2Ce2O7 proton conductor base material on SOFCs electrode is studied.A novel cathode material of M(M=Mo,Fe,Mn),Sr and Co co-doped La2Ce2O7 is prepared by sol-gel method.The single cells with La2Ce2O7 electrolyte are prepared to study the electrochemical performance of different cathode materials.The results show that the single cell of Ni-La2Ce2O7 | La2Ce2O7 | La2Ce2O7-LaMo0.2Sr0.4Co0 4Ce2O7-?get a best electrochemical property,which is 0.410 W/cm2 at 700 ?.