Sulfur Dioxide-Tolerant Bimetallic PtRu Catalyst toward Oxygen Electroreduction

Today’s proton exchange membrane fuel cells (PEMFCs) have achieved milestones in performance improvement and commercial launch. However, the wide deployment of PEMFCs is significantly limited by low stability, which is one of the greatest challenges for PEMFCs and is not only related to the material instability but also the poisoning contaminant in air. Tremendous efforts have been made on more stable catalysts, in contrast to the rare investigations touching contaminant-tolerant catalysts. Sulfur dioxide (SO 2 ) as a primary air contaminant may be fed along with air at the cathode, leading to Pt site deactivation. Therefore, SO 2 -tolerant electrocatalyst is urgently required toward oxygen reduction reaction (ORR). To address this challenge, we incorporate Ru that is free from SO 2 poisoning and synthesize PtRu alloy catalysts. Detailed investigations demonstrate that the Pt:Ru molar ratio is positively correlated with ORR activity but negatively correlated with SO 2 tolerance. Particularly, Pt 6 Ru 1 /C catalyst shows a competitive initial mass activity of 0.287 A mg –1 Pt and maintains 60% mass activity after SO 2 poisoning, much better than the commercial Pt/C (initial, 0.27 A mg –1 Pt; 30% remained). The engineered affinity between Pt and SO 2 in the presence of Ru is uncovered to account for the improvement. The Ru incorporation strategy is promising in improving the SO 2 tolerance of other state-of-the-art Pt-based catalysts.