Operatable and Efficient Mitigation Strategies for H2S Poisoning in Proton Exchange Membrane Fuel Cells: Releasing Pt Reactive Sites for Hydrogen Oxidation

The anode feed for hydrogen fuel cell electric vehicles (FCEVs) currently still relies on the reformed fuel that inevitably contains contaminants (e.g., CO, H2S, and NH3). As one of the most sensitive impurities, trace H2S in hydrogen significantly deteriorates the durability of proton exchange membrane fuel cells (PEMFCs), while there is still a lack of effective strategies to mitigate H2S poisoning in PEMFCs. Herein, we present two kinds of facile, operatable, and efficient strategies to mitigate a H2S-poisoned anode, with the aim of improving the durability of PEMFCs by releasing more Pt reactive sites for hydrogen oxidation reaction (HOR) catalysis. The first mitigation strategy is conducted by increasing the cell temperature temporarily when purging with pure hydrogen after H2S poisoning by means of accelerating H2S desorption on Pt sites under high temperatures and thus releasing more available Pt reactive sites for HOR catalysis. A higher temporary temperature leads to a larger recovery percentage of performance, outperforming the effect of the generally adopted pure hydrogen purging operation. Another mitigation strategy is called internal oxygen permeation, based on the oxidation of sulfur-adsorbed anode by compelling air diffusion through thin PEM via constructing a pressure differential between the cathode and the anode. The cell was found to be recovered more at a high pressure differential due to the fact that more sulfur species are oxidized by a larger content of permeated oxygen, showing similar to 88.7% performance recovery for 0.40 bar pressure differential. The proposed strategies with simplicity, operability, and resilience show promising potential in the application of long-term PEMFCs, which is critical for the durability improvement of FCEVs and cost reduction of hydrogen purification.

Automated summary

The anode of hydrogen fuel cell electric vehicles (FCEVs) is often contaminated with impurities like CO, H2S, and NH3, which greatly reduce the durability of proton exchange membrane fuel cells (PEMFCs). This study proposes two strategies, temporary temperature increase during hydrogen purging and internal oxygen permeation, to mitigate H2S poisoning in the anode and improve PEMFC durability. The first strategy accelerates the desorption of H2S and releases more Pt reactive sites for hydrogen oxidation reaction (HOR) catalysis, while the second strategy oxidizes sulfur on the anode using oxygen permeated through a thin PEM. These strategies have the potential to enhance the long-term performance of PEMFCs and reduce the cost of hydrogen purification for FCEVs.