Multiple Advance Diagnostics to Probe the Effect of Balance of Plant Materials on Fuel Cell Performance

Extensive research on fuel cell stack materials has led to advances in lower cost, high performing materials. With the decrease in the cost of stack materials, lowering the cost of the balance of plant (BOP) components has increased in importance. In order to decrease the overall cost of the automotive and stationary fuel cell systems and make them as competitive as possible, low-cost system component materials that provide similar function, performance and durability are needed. However, intelligently selecting low cost materials for application in polymer electrolyte membrane fuel cell (PEMFC) systems requires understanding the potential adverse effects that system contaminants may have on the fuel cell performance and durability. Limited work in this area has been conducted to-date.

There are many prospective BOP materials that can be used in fuel cell systems. Our material selection was based on the material’s physical properties (i.e., whether it will be stable in fuel cell operating conditions), commercial availability, cost and input from OEMs and fuel cell system manufacturer. Families of material chosen for the study include structural materials, elastomers for seals and (sub)gaskets, and assembly aids (adhesives, lubricants).

Two types of low cost structural plastic materials – a polythlalamide and a polyamide – were studied. Leachates obtained from these plastics were a mixture of organics, inorganics, and ions and were introduced to a working fuel cell to determine their effect on the fuel cells performance. Organics that were identified in the leachate solutions via gas chromatography mass spectrometry (GCMS) include 1,8 Diazacyclotetradecane-2,7-dione (DCTDD), aniline, and caprolactam. These plastic materials also released anions: chloride, phosphate, nitrates, and sulfates. In-situmeasurements such as infusion, cyclic voltammetry, impedance spectroscopy, and I-V curves were carried out to better characterize the contaminants effects of the mixtures of compounds in the extracts. The effect of the individual organic model compound (caprolactam), anion (sulfate) and mixtures of the two species were also studied to better understand the contamination mechanisms of specific species and their interaction with one another.

This presentation will also briefly describe the ex-situ electrochemical quartz crystal microbalance (EQCMB) technique used to study the adsorption effect of organic compounds, derived from system contaminants, on Pt surface. EQCMB was used to measure the change in mass of the electrode as a function of potential.

The authors would like to acknowledge funding from the U.S. Department of Energy EERE Fuel Cell Technologies Office, under Contract No. AC36-08GO28308 with the National Renewable Energy Laboratory and collaborations with colleagues at GM and 3M. Structural plastic materials were provided by GM and membrane degradation products for this study were provided by 3M.