A Pathway towards Pt-free Cathodes in High-Temperature Proton Exchange Membrane Fuel Cells

Abstract

The high temperature proton exchange membrane fuel cell (HT-PEMFC) has several advantages compared to its low temperature (LT) counterpart. The typical operation temperature of 160 °C enables an easier heat management, and the omission of humidification. However, due to the partial blocking of the cathodic and anodic Pt catalyst by phosphates from the phosphoric acid-doped membrane, higher catalyst loadings compared to LT-PEMFC of 0.86 mgPt cm-2 per electrode are commonly employed.[1] To increase the competitiveness of HT-PEMFCs implementation of Fe-N-Cs is a promising option for reduction of catalyst costs. In this study, we give an overview about the application of different Fe-N-C catalysts in Pt free HT-PEMFC cathodes.[2] Moreover, we show their application in hybrid PtNi/C+Fe N C cathodes.[1] The complete replacement of Pt catalyst by Fe N C in the cathode results in low performance[2] and a strong voltage decay within the first 60 hours of HT-PEMFC operation. In contrast, a hybrid MEA with reduced Pt-loading displayed a more comparable performance to commercial MEA (Celtec®-P1200) and constant voltage over 60 h. Furthermore, it was found that the typical activation procedure of HT-PEMFC MEAs (around 60 h constant load) is not sufficient for hybrid MEAs. There, a voltage increase over the first 240 h of operation was observed.[1] These results give the basis for further optimization of Pt-free Fe N C electrodes. Furthermore, the potential of hybrid MEAs for Pt-loading reduction in HT-PEMFC is pointed out.