Silver-modified Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) as cathodes for a proton conducting solid-oxide fuel cell

摘要

Electrochemical performance of silver-modified Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) (BSCF-Ag) as oxygen reduction electrodes for a protonic intermediate-temperature solid-oxide fuel cell (SOFC-H~+) with BaZr_(0.1)Ce_(0.8)Y_(0.1)O_3 (BZCY) electrolyte was investigated. The BSCF-Ag electrodes were prepared by impregnating the porous BSCF electrode with AgNO_3 solution followed by reducing with hydrazine and then firing at 850 ℃ for 1 h. The 3 wt.% silver-modified BSCF (BSCF-3Ag) electrode showed an area specific resistance of 0.25 n cm~2 at 650 ℃ in dry air, compared to around 0.55 Ω cm~2 for a pure BSCF electrode. The activation energy was also reduced from 119 kJ mor~(-1) for BSCF to only 84 kJ mol~(-1) for BSCF-3Ag. Anode-supported SOFC-H~+ with a BZCY electrolyte and a BSCF-3Ag cathode was fabricated. Peak power density up to 595 mW cm~(-2) was achieved at 750 ℃ for a cell with 35 μm thick electrolyte operating on hydrogen fuel, higher than around 485 mW cm~(-2) for a similar cell with BSCF cathode. However, at reduced temperatures, water had a negative effect on the oxygen reduction over BSCF-Ag electrode, as a result, a worse cell performance was observed for the cell with BSCF-3Ag electrode than that with pure BSCF electrode at 600 ℃.