Durability of PtCo/C Cathode Catalyst Layers Subjected to Accelerated Stress Testing

In this paper we evaluate the durability of two PtCo/C alloy catalysts that have different initial particle sizes by using accelerated stress tests. The durability test results are compared with a commercially available Pt/C catalyst. The implications of using PtCo/C alloy catalysts are discussed, with results presented from TEM, SEM, XRF, XRD and electrochemical testing. The initial ECSAs of the PtCo/C catalysts are lower than Pt/C, however by the end of the AST, the ECSAs are nearly identical as the particle sizes all approach approximately 5.5 nm. The mass activity of PtCo/C catalysts is higher than Pt/C, thus leading to higher kinetic performance. The durability and activity of PtCo/C catalysts was found to be comparable or better than that of the Pt/C based catalysts. However, gradual Co leaching from the alloy structure continues to be an issue. Co was found to essentially equilibrate between the catalyst layer and the membrane.