Ambient contaminants, e.g., sulfur dioxide (SO 2 ), lead to severe Pt deactivation and performance loss of practical proton exchange membrane (PEM) fuel cells, which need to be removed immediately. We herein find that only partially adsorbed SO 2 can be oxidized and removed at up to 1.5 V, even for a longer period. By contrast, interestingly, dynamic potential scanning for several cycles (usually > 8) can gradually regenerate poisoned Pt/C. In situ infrared spectroscopy demonstrates that parallel-bonded SO 2 is forbidden to be electro-oxidized at a high potential but can be converted to easily oxidized atop-bonded and bridge-bonded SO 2 at a low potential. Due to the potential-dependent transformation, SO 2 is gradually oxidized and removed under dynamic potential scanning instead of potentiostatic polarization. Based on this regeneration mechanism, we propose a square wave-based protocol to completely regenerate SO 2 -poisoned Pt surfaces within unprecedented three cycles.
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Liu et al. (2021) studied this question.
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