Potassium-Assisted Chromium Transport in Solid Oxide Fuel Cells

Chromium transport from stainless steel current collectors to the cathode can be a route for rapid performance degradation in solid oxide fuel cells. Typical volatile chromium species, such as CrC 2 (OH) 2 , are manageable; however, volatile species with higher vapor pressures may play a significant role in chromium transport and deposition. One such species, K 2 CrO 4 , is readily formed by the chemical reaction between KOH or K 2 O and Cr 2 O 3 and electrochemically reduced along triple-phase boundaries. The vapor pressure and expected chromium deposition rate of potassium chromate and chromium oxyhydroxide phases are compared to the long-term electrical performance of anode-supported SOFCs. Experimental evidence supports the findings that potassium and chromium, in the presence of an applied electric field, greatly enhances the degradation of cell performance (-85% in 500 h).