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 CrO2(OH)(2), are manageable; however, volatile species with higher vapor pressures may play a significant role in chromium transport and deposition. One such species, K2CrO4, is readily formed by the chemical reaction between KOH or K2O and Cr2O3 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).