Preparation And Electrochemical Performance Of A New Structured Low Temperature SOFC With BZY Electrolyte

The future society will face the problem of exhaustion offossil fuel.As more and more countries move towards industrialization and world population growth,the demand for energy is increasing.The development of clean and renewable energy conversion device is the main battlefield in the field of energy science and technology.Solid oxide fuel cell(SOFC)is an electrochemical device that can directly convert chemical energy into electrical energy.It is one of the most promising and effective energy production systems to reduce pollutant emissions,which has attracted more and more attention in recent years.In the past ten years,scientists in the SOFC field have generally believed that reducing the running temperature of SOFC is conducive to its commercialization.The ionic conductivity of the existing SOFC electrolytes at low temperatures(300～600℃)can not meet the needs of the high power density output of the cell.Therefore,it is imperative to develop new electrolyte materials or new electrolyte structures with high conductivity at low temperature.In recent years,a kind of electrolyte structure which has not been densified by high-temperature sintering has been widely studied.Such electrolyte structure can be obtained by high pressure compaction and sintered at the cell operating temperature.It can achieve very high ionic conductivity,but its ionic conduction mechanism has not been reported in detail.BaZrO3 is a perovskite type oxide with high temperature proton conductivity.It has relatively high proton conductivity at 600℃,but it still can’t meet the need of low temperature SOFC.In this paper,a single cell of foam Ni-NCAL/BZY/NCAL-foam Ni with novel BZY electrolyte structure was prepared by co-pressure method,using BaZr0.9Y0.1O3-α(BZY)and LiNi0.8Co0.15Al0.05O2(NCAL)-pasted foamNi as electrolyte and electrodes,respectively.The ion conduction mechanism of new BZY electrolyte was investigated by the cell electrochemical performance test,ion filtration experiments of bi-layered electrolyte cell,microstructure characterization of the cell and the characterization of BZY surface properties.The details are as follows:(1)BaZr0.9Y0.1O3-α powders were synthesized by sol-gel method,and the powers were obtained after respectively sintering at 1000 and 1200℃ for 5 h.XRD results show that BZY with a calcination temperature of 1200℃ has a good perovskite structure and no apparent additional phase is generated.(2)The single cell with a.configuration of foam Ni-NCAL/BZY/NCAL-foam Ni were fabricated by the co-pressing method using the BZY calcined at 1200℃ as the electrolyte,The maximum power density were 735.6,538.4 and 326.4 mW·cm-2 at 550,500 and 450℃ in H2,which aremuch higher than the results obtained using traditional SOFCs with the same thickness of high temperature densified BZY electrolyte.The ionic conductivity of the novelstructure BZY electrolyte prepared in this study were 0.42,0.50 and 0.56 S·cm-1at 550,500 and 450℃,whichare much higher than that of the conventional high temperature densified BZY electrolyte.The activation energy of ionic conduction of the BZY electrolyte prepared in this study is 0.23 eV,which is much lower than that of traditional oxygen ion or proton conduction.(3)In order to clarify the ion conductivity mechanism of the novel structure BZY electrolyte prepared in this paper,a densified pure oxygen ion conductor Ce0.9Gd0.1O2 pellet was used as an ion filter,and the single cell foam Ni-NCAL/GDC/BZY/NCAL-foam Niwith the GDC/BZY double layer electrolyte was prepared.The densified GDC pellet was pressed by isostatic pressing and sintered at 1550 ℃,BZY electrolyte was pressed by 360 MPa co-pressing method.Then sintered at the temperature of cell performance testing.The maximum power density of the cell with BZY/GDC bi-layered electrolyte was 47.5 mW·cm-2 at 550℃ in H2.It is concluded that oxygen ions are the main carriers in the novel structure BZY electrolyte according to the ion filtration experiments and the change of EIS results of the foam Ni-NCAL/BZY/NCAL-foam Ni cell in different atmospheres.(4)According to the SEM microstructure of BZY electrolyte,the results of TGA,XPS and FTIR of the raw BZY powderand the BZY powder after performance test,we believe that in the novel BZY electrolyte structure,the interface between BZY particles and its surface are the main channels for the high-speed conduction of oxygen ions.A detailed description of the ionic conduction mechanism for the BZY electrolyte still requires further investigation.