Characteristics of Metallic Bipolar Plate for Polymer Electrolyte Membrane Fuel Cells

Abstract

The bipolar plate is one of the most significant key components in polymer electrolyte membrane fuel cells (PEMFCs). Bipolar plate (BPP) weight and cost are determining factor for future commercialisation of PEMFC technology. To overcome this major hurdle, metallic bipolar plates are used as a BPP in large number of commercial PEMFCs due to their advantages such as excellent mechanical strength, good electrical and thermal conductivities, low cost, ease of fabrication, gas impermeability, and possibility to make thin plates [1, 2]. However, corrosion remains a major anxiety for metallic bipolar plates use in real PEMFC operating conditions. Further, the formation of passivation layers reduces not only the electrical conductivity but also the overall performance. The aim of this present research is to characterise metallic bipolar plate with respect to corrosion behaviour, surface area and roughness changes and its level of success to meet the DOE requirements for BPPs. Especially, electrochemical stability was investigated in terms of corrosion measurements within a three electrode cell system. Active exposure area of 1 cm2 bipolar plate material was used as working electrode (WE). A platinum wire with an activated carbon felt, and reversible hydrogen electrode employed as a counter electrode (CE), and reference electrode (RE), respectively. Bipolar plates were subjected to chemical storage in 0.5 M H2SO4 at 80 ºC as a function of time. Further, electrochemical stability were evaluated in term of potentiostatic conditions such as open circuit potential (OCV), anodic and cathodic polarisation conditions. Finally, a corrosion analysis is presented using atomic force microscopy (AFM), confocal microscopy and/or µ-computed tomography (µ-CT) as well as inductively coupled plasma with mass spectrometry (ICP-MS) as an attempt to know the surface area changes of corrosion in metallic bipolar plates and their degradation products in acid. Figure 1: Three-electrode set-up for corrosion measurements (left), AFM picture of metallic BPP (right) Figure 1