Impact of Structural Plastics as Balance of Plant Components on Fuel Cell Performance

Structural plastics are a primary class of material used for integrating the balance of plant (BoP) components into a fuel cell system that is both compact and robust for automotive applications. It has been approximated that the cost of the BoP is roughly 50% of the total cost to a fuel cell system [1]. Therefore, it is critical to select grades of structural plastics that meet the mechanical properties and cost targets for automotive system and do not negatively impact the performance or durability of the fuel cell stacks. The integration of balance of plant components to feed the reactant and coolant streams to the stacks creates a significant amount of wetted surface. Hence, GM has developed a series of screening protocols to assess the compatibility of prospective BoP materials in a fuel cell system. [2-4] The objective of these series of experiments is to understand if a perspective BoP material adversely affects the fuel cell electrode or the membrane and whether these effects are recoverable under normal automotive operating conditions. The experiments include soaking BoP materials at temperature in DI water to extract a ‘soup’ of potential contaminants from the material. The contamination soup is then used to screen the material. Membrane and electrodes are screened for adverse interactions with membrane conductivity and cyclic voltammetry (CV), respectively. Next the ‘soup’ is infused into an operating fuel cell to measure the impact on performance. Additionally the extract solution is characterized analytically to understand the component species. Ultimately the screening procedure was successful in providing a rapid screening tool to determine if these materials can adversely affect the performance of a fuel cell [3-7]. While these protocols are effective to screen out bad grades of material, increased effort is needed to quantify the impact of relatively good grades of plastics on the fuel cell performance. Figure 1 compares impact of contamination by infusing an extract solution from a structural plastic to a baseline case wherein the cell was infused with de-ionized (DI) water by plotting the measured cell voltage and high frequency resistance (HFR) at a fixed current density of 0.2 A/cm. This work will focus on understanding the sensitivity of the observed voltage loss to operating conditions and elucidate the source of the voltage loss observed.