Yttrium doped cerium oxide as free radical scavenger for proton exchange membrane fuel cells

Yttrium doped cerium oxide (CeO2·Y2O3) was studied as a free radical scavenger for PEMFCs. MEA with CeO2·Y2O3 was compared with MEAs with CeO2 and without free radical scavenger. MEAs before and after 50 h of open circuit voltage hold accelerated stress test show better performance retention with CeO2·Y2O3 than CeO2. MEAs with CeO2·Y2O3 and CeO2 perform better than the pristine MEA without free radical scavenger. ECSA, MA, and EIS of the MEAs were analyzed to confirm the effect of free radical scavengers on MEA performance and durability. XRF confirmed the improved Ce ions retention in MEAs with CeO2·Y2O3 than pure CeO2, indicating improved stability of Ce ions after doping with Yttrium. Effluents from the anode and cathode of the fuel cells were collected and analyzed by fluoride ion selective electrodes at 25 h and 50 h of the accelerated stress test. The fuel cell with CeO2·Y2O3 as a free radical scavenger has the lowest fluoride emission rate. Furthermore, the ex-situ Fenton study combined with ICP-MS analysis shows better stability of Ce in CeO2·Y2O3. This study indicates that yttrium-doped cerium oxide has better stability against dissolution and enhances the stability of polymer components against free radicals compared with CeO2, which will benefit the long-term durability of the PEMFCs.