PtCo, a Durable Catalyst for Automotive PEMFC?

Abstract

Carbon supported Pt and PtCo alloy cathodes have been evaluated under the DoE proscribed accelerated MEA durability protocol (0.7 - 0.9 V iR free, square wave cycle, H2/air). The Pt MEA showed reasonable stability up to 2500 cycles, after which significant performance loss was observed. Post mortem analysis indicated that this was due to Pt sintering and dissolution. The PtCo MEA showed similar stability up to 2500 cycles showing a mass activity of twice that of the Pt MEA. However, after this, activity loss was observed to a value similar to pure Pt, without significant loss in electrochemical area. The MEA was tested to 83,000 cycles with only a gradual further activity loss. Post-mortem analysis showed only modest Pt sintering and loss of Pt into the membrane. This early loss of PtCo activity has been correlated with surface loss of Co through activity testing of acid pre-leached catalysts.