Investigation of Microstructure and Pt Distribution in Catalyst Layer after Accelerated Degradation Test in PEMFC

Abstract

The membrane electrode assembly (MEA) is the key part of the Proton Exchange Membrane Fuel Cell (PEMFC). Except applying the high efficiency catalyst, to improve the Pt efficiency for oxygen reduction reaction (ORR) by optimizing the microstructure of MEA is also a key point to achieve the high performance and longevity of the low Pt loading MEA. However, it is still difficult to correlate the microstructure of the MEA, especially the microstructure of the catalyst layer (CL) and the performance of the MEA due to the complex physical and chemical processes in the catalyst layer. In this study, we reported our work on the low Pt loading MEA and the preliminary results of the accelerated degradation test (ADT) of the MEA. The ADT test was conducted under the DOE’s ADT protocol. SEM, associated with back scattered electron imaging (BSE), EDX mapping, EDX linear scan technique, was applied. The spatial distribution of aggregated Pt particles at cathode of our self-made MEAs (Pt loading at anode is kept at 0.05mg/cm2, the Pt loading at cathode is 0.05, 0.15, 0.55mg/cm2 respectively.) was revealed. It suggested three different region of Pt accumulation – the interface between the membrane and the catalyst layer, the main part of the catalyst layer, and the interface between the catalyst layer and the micro porous carbon layer. The significant Pt aggregation happened at the two interface area of the catalyst layer. This implies the different spatial utilization of the Pt catalyst in the catalyst layer. For clarity, Fig 1 shows the BSE images of MEA cathode with Pt loading of 0.1mg/cm2 and the voltage degradation of the MEA during the ADT test. The detailed discussion of the spatial distribution of aggregated Pt particles will be presented at the symposium. Figure 1