Quantification of effects of performance recovery procedures for polymer electrolyte membrane fuel cells

Abstract To distinguish and mitigate the reversible and irreversible performance degradation of polymer electrolyte membrane fuel cells (PEMFCs), the evaluation and investigation of recovery procedures are of great importance. In this work, a methodology for quantification of recovery of reversible voltage losses is presented taken a durability test containing well-defined operation periods interrupted by two recovery procedures as an example. Each recovery procedure is characterized by polarization curves and electrochemical impedance spectroscopy (EIS). To evaluate the influence of the two used recovery procedures on the fuel cell performance, four factors are considered: (i) absolute recovered voltage, (ii) absolute non-recovered voltage, (iii) relative recovery related to previous operation period, and (iv) relative recovery related to the beginning of the test. The results show that voltage recovery quantified using polarization curves and voltage data logged during load cycling lead to the same result. Hence, to briefly assess the efficiency of a recovery procedure in a (narrow) current density range covered by the used load cycling profile, in-depth electrochemical characterization is not required. Moreover, EIS data were used to determine the main mechanisms leading to recovery. By this means, weaknesses of specific recovery procedures can be identified in order to propose specific improvements.