Investigation of Different Electrochemical Corrosion Treatments on Bipolar Plates for High and Low Temperature Polymer Electrolyte Membrane Fuel Cell Application

Abstract

Bipolar plates (BPP) play an important role in a fuel cell system.1 They take on several tasks, such as distributing the reactants homogeneously over the active membrane-electrode-assembly surface, electrical and thermal conductivity and preventing leakages.1-2 The aim of this present research is to investigate the corrosion behaviour of BPP materials for high and low temperature (HT and LT) polymer electrolyte membrane fuel cell (PEMFC) applications. For this study BPP materials were investigated by different electrochemical corrosion methods using a three-electrode cell setup shown in figure 1. The three-electrode cell setup was utilised for bipolar plates corrosion at the DLR institute before.3 As working electrode a BPP sample with an active area of 1 cm2, as counter electrode a carbon-rod and as reference electrode a reversible hydrogen electrode (RHE) was used. To investigate the electrochemical stability of the BPP for use in HT- and LT-PEMFC potentiostatic conditions such as open circuit, anodic and cathodic potentials were recorded in conc. (~14.6 M) phosphoric acid (PA) and 0.5 M sulfuric acid, respectively. Cyclic voltammograms (CV) were plotted before and after the above mentioned potentiostatic treatments to evaluate the oxidation resistance behaviour of the BPP. Due to stability limitations of the set-up, the electrochemical measurements were carried out at room temperature. Therefore BPP for use in HT-PEMFC were chemical aged at 160 °C in conc. PA before electrochemical corrosion treatments to achieve good agreement with HT-PEMFC conditions. Figure 2 shows an example of the CVs of pristine, after chemical and electrochemical aged BPP for use in HT-PEMFC. Typical quinone/hydroquinone peaks can be observed between 0.6 and 0.7 VRHE. The double layer capacitance is increasing after each aging step which can be explained by the oxidation of carbon surface leading to BPP corrosion. Further investigations with methods like scanning electron microscopy, confocal microscopy, µ-computed tomography and titration will be shown to correlate surface area changes and acid uptake with corrosion measurement results. References Hermann, A.; Chaudhuri, T.; Spagnol, P., Bipolar plates for PEM fuel cells: A review. Int. J. Hydrogen Energy 2005, 30, 1297-1302. Antunes, R. A.; de Oliveira, M. C. L.; Ett, G.; Ett, V., Carbon materials in composite bipolar plates for polymer electrolyte membrane fuel cells: A review of the main challenges to improve electrical performance. J. Power Sources 2011, 196 (6), 2945-2961. Pilinski, N.; Käding, C.; Dushina, A.; Hickmann, T.; Dyck, A.; Wagner, P., Investigation of Corrosion Methods for Bipolar Plates for High Temperature Polymer Electrolyte Membrane Fuel Cell Application. Energies (Open Access Journal) 2020, 13 (1), 235. Figure 1