Study On Solid Reaction And Properties Of Composite Electrolyte Bace_0.8Y_0.2O_3-δ-Ce_0.8Gd_0.2O_1.9 For Intermediate Temperature Solid Oxide Fuel Cells

Solid oxide fuel cell (SOFC) can convert chemical energy of fuel into electrical energy directly and have been a major concern in recent years in terms of high energy conversion efficiency and environmental friendliness. As the core material of SOFC, performance of electrolyte directly affects the output power of the cell. In this study, BaCeO3 doped electrolyte and CeO2 doped electrolyte were synthesized via citric acide-nitrate gel combustion method. Then, they were mixed by wet milling and get composite electrolyte to study the effect of doped elements Y and Gd on solid reaction of composite electrolyte BaCe0.8Y0.2O3-δ-Ce0.8Gd0.201.9; XRD, SEM, EDS, AC impedance spectroscopy and the single cell electrochemical performance of composite electrolyte BaCe0.8Y0.2O3-δ-Ce0.8Gd0.2O1.9 (BCY-GDC) with different proportion of two phase and different sintering holding time were studied. The influence factors and rules of solid phase reaction and properties of composite electrolyte BaCe0.8Y0.2O3-s-Ceo.8Gd0.2O1.9 were discussed to get composite electrolyte material with excellent electrochemical performance.The results of effects of doped elements Y and Gd on solid phase reaction of BaCeo.8Y0.2O3-δ-Ceo.8Gd0.201.9 show that:only any phase or two phases of BaCeO3-CeO2 doping elements Y, Gd can prompt apperance of single-phase perovskite structure on the electrolyte surface and have the ionic conduction ability. BCY-GDC formed by two phases of BaCeO3-CeO2 doped has the best electrical conductivity.The research results of composite electrolyte formed by mixing BaCe0.8Y0.203-δ and Ce0.8Gd0.2O1.9 with different proportion show that:When the BCY content was higher than 30%, solid phase reaction occurs on the surface of the composite electrolyte, then a single-phase with perovskite structure produces. The ionic conductivity of composite electrolyte at the temperature of 700 ℃ is associated with BCY content:when the molar ratio of BCY:GDC is 6:4, the electrical conductivity of composite electrolyte is the minimum, about 3.94 mS/cm; when the molar ratio of BCY:GDC is 3:7, the electrical conductivity of composite electrolyte is the highest, about 11.48 mS/cm. The open circuit voltage of Ni-BCY-GDC|BCY-GDC|LSCF single cell are all higher than that of Ni-GDC|GDC|LSCF single cell, With the decreas of BCY content, the OCV of the cell reduces. When the molar ratio of BCY:GDC is 3:7, its single cell has the best performance.The research results of the composite electrolyte with molar ratio BCY:GDC of 3:7 calcided under 1550 ℃ at different times show that:the fluorite structure peak at the surface of the composite electrolyte decrease when calciding holding time from 1 to 7 hours, however, while calciding holding time from 10 to 13 hours, single-phase of fluorite structure formedon the surface of the composite electrolyte. With the increase of holding time, the grain size of composite electrolyte increases, but no significant change in conductivity. When the holding time is 1h, the Ni-BCY-GDC|BCY-GDC|LSCF single cell has the highest performance. When working temperature is 700 ℃, the maximum power density of 866 mW/cm2 is 1.7 times higher than that of Ni-GDC|GDC|LSCF single cell.