Performance degradation and recovery effect of direct formic acid fuel cells using a palladium anode catalyst

Direct formic acid fuel cells (DFAFCs) using palladium (Pd) as an anode catalyst exhibit high performance. However, with use of the Pd, the performance of DFAFC is rapidly reduced while operation. To evaluate correlation between the undesirable effects of Pd such as deactivation and agglomerization and DFAFC performance, and to find out the best recovery condition of cell performance, 4-step electrochemical tests are consecutively implemented under the fixed cell voltages ranged from 0.2 V to 0.8 V; initial polarization, intentional degradation (current vs. time curve with fixed cell voltage), cyclic voltage scan-based reactivation, and polarization. According to these test results, performance degradation of DFAFC was almost similar after the intentional degradation test. However, after the reactivation test, performance of DFAFC degraded at 0.4 V was well-recovered, while those degraded at higher than 0.6 V were not sufficiently recovered. To characterize the effect of Pd on DFAFC performance, characterizations such as zeta potential, TEM, electrochemical impedance spectroscopy (EIS) and cyclic voltammogram (CV) were carried out. Based on the results, it was found that under 0.4 V, Pd particles were well distributed and its charge transfer resistance (Rct) was low, while Pd particles were agglomerated and Rct increased at higher than 0.6 V. Eventually, it is concluded that disparities in Pd particle distribution and Pd poisoning affect performance degradation and recovery of DFAFC.