Stability of Pt/MWCNT Electrocatalyst during Startup and Shutdown Cycles: Voltage Degradation in PEM Fuel Cells

Abstract

Proton exchange membrane fuel cells (PEMFC) are interesting candidates for automotive applications. Today’s challenge is to increase the mass activity from pure platinum of currently 0.12 A/mgPt to 0.44 A/mgPt at 0.9 V (iR-free) vs. RHE, and to enhance the durability with a high stability in startup/shutdown (SU/SD) procedures.[1-3] During SU/SD cycles, the cathode voltage of a PEMFC can increase up to 1.5 V vs. RHE which accelerates the carbon corrosion drastically. These huge carbon corrosion rates lead to a complete loss of the electrode structure, and therefore to a dramatic loss of performance. In order to reduce carbon corrosion, the chemically more stable multi walled carbon nanotubes (MWCNTs) can be used as catalyst support. The higher stability in comparison to conventional catalyst material was already demonstrated in rotating disk electrode (RDE) experiments.[4] Here, the electrocatalyst was tested with two different cycling protocols, (I) 0.5 to 1.0 V vs. RHE (10.000 cycles, 50 mV/s) and (II) 0.5 to 1.5 V vs. RHE (2.000 cycles, 50 mV/s) in deaerated electrolyte (0.1 M HClO4) at room temperature.In this contribution, we present our recent results regarding the stability of Pt/MWCNTs under real hydrogen-air front experiments in 50 cm2 single cell. During this test, the anode side is successively flushed with hydrogen or air while the cathode side is continuously purged with air.N. A., U. K. and T. T. acknowledge efzn for financial support.Literature[1] Department of Energy - Multi Year Research and Development Plan (2011), Table 3.4.13 Technical Targets: Electrocatalysts for Transportation Applications.[2] Oezaslan, M.; Hasché, F.; Strasser, P., The Journal of Physical Chemistry Letters 2013, 4 (19), 3273-3291.[3] Yu, P. T.; Gu, W.; Makharia, R.; Wagner, F. T.; Gasteiger, H. A., ECS Transactions 2006, 3 (1), 797-809.[4] Hasché, F.; Oezaslan, M.; Strasser, P., Physical Chemistry Chemical Physics 2010, 12 (46), 15251-15258.