Improved electrochemical performance and thermal compatibility of Fe- and Cu-doped SmBaCo_2O_(5+δ)Ce_(o.9)Gd_(0.1)O_(1.95) composite cathode for intermediate-temperature solid oxide fuel cells

摘要

Fe- and Cu-doped SmBaCo_2O_(5+δ) (FC-SBCO)-Ce_(0.9)Gd_(0.1) O_(1.95) (CGO) composites with various CGO contents (0-40wt.%) are investigated as new cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) based on a Ce_(0.9)Gd_(0.1)O_(1.95) electrolyte. The effect of CGO incorporation on the thermal expansion coefficient (TEC), electrochemical properties and thermal stability of the FC-SBCO-CGO composites is investigated. A composite cathode of 30wt.% CGO-70wt.% FC-SBCO (CS30-70) coated on a Ce_(0.9)Gd_(0.1)O_(1.95) electrolyte shows the lowest area specific resistance (ASR), i.e., 0.049 Ω cm~2 at 700 C. The TEC of the CS30-70 cathode is 14.1 x 10~(-6) C~(-1) up to 900℃, which is a lower value than that of the FC-SBCO (16.6 x 10~(-6)℃~(-1) counterpart. Long-term thermal stability and thermal cycle tests of the CS30-70 cathode are performed. Stable ARS values are observed during both type of test. An electrolyte-supported (300-μm thick) single-cell configuration of CS30-70/CGO/Ni-CGO delivers a maximum power density of 535 mWcm~(-2) at 700℃.The unique composite composition of CS30-70 demonstrates improved electrochemical performance and good thermal stability for IT-SOFCs.