| Energy shortage and low utilization-ratio are current situation in our country for energy-using. Recently, solid oxide fuel cells (SOFCs) have received widespread attentions and have been hailed as prospective green-energy star due to its high energy conversion efficiency, environment friendly, fuel adaptability etc. However, operating up to1000hinders further development of traditional SOFCs. It became the main direction for future SOFCs researches to reduce the high operation temperature. Besides, Cathode materials have became a determinant factor for the performance of LT-SOFCs as a consequence of higher activation energy of cathode reaction (reduction of oxygen) and thus rapid increasing of cathode polarization resistance with temperature lowered. With high mixed ionic-electronic conductivity and excellent catalytic property for oxygen-reduction, ABO3type perovskite oxides have been treated as promising cathode materials for LT-SOFCs.The B-site doping BaFeO3.5cathode material:BaFe0.6Ce0.1Co0.3O3-δ (BFCC) powder was synthesized by the modified Pechini method. It can be known from XRD that BFCC is a single perovskite phase. And its thermal expansion coefficient (TEC) matches with ionic conductor SDC very well between400and600C. Besides, the electronic conductivity is as desired. This paper mainly researches the electrochemical performance of BFCC as cathode for O-SOFCs and H-SOFCs respectively.Firstly, the electrochemical performance of BFCC as cathode for O-SOFCs have been tested.(1) A symmetric cell BFCC/SDC/BFCC with SDC as electrolyte, BFCC as both anode and cathode has been fabricated. The EIS spectra of the symmetric cell have been tested using Electrochemical Workstation, in which interface resistance between cathode and electrolyte is only0.042Ω cm2at700℃has been read.(2) Moreover, an anode-supported single cell with SDC as electrolyte, NiO-SDC as anode and BFCC as cathode has also been fabricated. The electrochemical properties of the single cell has been tested in a tubular furnace from550℃to700℃with hydrogen (～3%H2O) as fuel and oxygen as oxidant, respectively. The results show that the maximum power density of the single cell reaches1368.4mW cm-2at700℃.Then, the electrochemical performance of BFCC and its composite materials as cathode for H-SOFCs have been tested respectively. Three single cells have been assembled, all with NiO-BZCYYb as anode, BZCYYb as electrolyte while one with pure BFCC, another with BFCC-BZCYYb (0.8:0.2by weight) and the third one with BFCC-BZCYYb (0.6:0.4by weight) as cathode, respectively. Electrochemical performance of the three single cells NiO-BZCYYb/BZCYYb/BFCC,NiO-BZCYYb/BZCYYb/BFCC-BZCYYb(0.8:0.2), NiO-BZCYYb/BZCYYb/BFCC-BZCYYb(0.6:0.4) have been tested in alike conditions with above O-SOFCs, respectively. The maximum power density of the three single cells achieves517.1mW cm-2,244.7 mW cm-2and455.7mW cm-2at700C, respectively. Polarization resistances of the three cells are0.085Ω cm2,0.073Ω cm2,0.063Ω cm2at700℃, respectively, on the basis of EIS spectra.Considering the performance of BFCC as cathode for O-SOFCs and H-SOFCs, respectively. It is clear that BFCC is a novel efficient cathode material for LT-SOFCs and deserves further research. |
