While these and other mitigation strategies have largely reduced SUSD damage on the cathode, recent studies suggest that SUSD events might also lead to voltage losses due to anode degradation.4 Mittermeier et al. proposed that the potential cycling of the anode during H2/air front passage from ≈0 V (H2-filled) to ≈1 V (air-filled) might be the main reason for anode corrosion during SUSD. Since this degradation mechanism would scale with the number of H2/air front passages, its impact on the overall SUSD damage will become more pronounced as the cathode is protected by other SUSD mitigation methods (e.g., use of graphitized carbon supports, SUSD at low temperatures, short H2/air front residence times) and upon the implementation of ultra-low anode loadings (<0.05 mgPt/cm2).
Aim of this study is to characterize the SUSD induced anode degradation mechanisms and to quantify the extents of carbon support corrosion and the loss of electrochemical surface area (ECSA). For example, ECSA losses of anode and cathode upon extended SUSD cycles are shown in Figure 1a and b, respectively. Furthermore, we will examine the feasibility of an accelerated test to quantify anode SUSD degradation based on voltage cycling between ≈0 and ≈1 V under N2. Finally, based on these data, we will project the influence of anode SUSD degradation in the case of anodes with ultra-low Pt-loadings (< 0.05 mgPt cm-2) based on pure Pt or Pt-alloy anode catalysts.
The authors of this work thank David Fischermeier for preliminary tests in an early stage of this study.
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3 Y. Yu, H. Li, H. Wang, X.-Z. Yuan, G. Wang, and M. Pan, Journal of Power Sources, 205, 10 (2012).