Influences of Contact Pressure on the Performances of Polymer Electrolyte Fuel Cells

Fuel cells face major challenges in sustaining the laboratory-scale performance during the scale up. The contact resistance mainly arises from the dimensional mismatch between gasket and gas diffusion layer during scale up, which may cause diminution in performance. In the present work, experiment as well as modelling is carried out for different combinations of clamping force and gasket thickness. The polarisation behaviours of PEFCs configured under different clamping torques and gasket thicknesses are analysed. The combination of 0.3？mm gasket and 0.3？mm GDL under 3？Nm and 5？Nm clamping forces offers 480？m？？cm2 and 148？m？？cm2 contact resistances, respectively. The configurations under 3？Nm and 5？Nm clamping torques with 0.2？mm thick gasket offer contact resistances as low as 23？m？？cm2 and 11？m？？cm2, respectively. The polarisation behaviour obtained from the experiment of such configurations is found to be in good agreement with the modelling results. 1. Introduction Fuel cells show great promises in the field of portable, transport and stationary applications [1–3]. They show excellent current voltage characteristics in laboratory-scale cell. However, researchers encounter challenges during scale up due to the heterogeneous local performances inside the fuel cells [4–6]. The local performance is influenced by the operating conditions such as humidity, temperature, and reactant pressure [7–9]. Assembly parameters such as clamping force and gasket thickness influence the local and overall performances. The contact resistance that mainly arises from the dimensional mismatch between the gasket and gas diffusion layer (GDL) plays a significant role in overall performance of the polymer electrolyte fuel cell. Among different components, mainly matching in the thicknesses of the gasket and the GDL is important to achieve best performance in the fuel cells. Mismatch may lead to the following problems as illustrated in Figure 1.(i)？Thinner gasket may lead to sealing problem causing safety issue. In addition to that, the cell will be facing mass transport-related losses ( Figure 1(b)).(ii)On the other hand, thicker gasket may result in poor contact between the bipolar plate (BPP) and the GDL, causing a rise in the contact resistance in the cell which will be reflected on the ohmic region of the current voltage characteristics (Figure 1(c)). Figure 1: Schematic diagram of a half-cell configuration: (a) optimum, (b) with thinner gasket, and (c) with thicker gasket. Hence, it is important to achieve optimum matching between the gasket and the GDL used in polymer