Effect of Water Conductivity on Proton Exchange Membrane (PEM) Catalyst Durability Using Thermal Degradation Resistant Polymer Membranes in Combat Applications

Abstract

The U.S. Army is taking an increasing interest in fuel cell technology as vehicles require more electrical power to support additional capabilities. One challenge the U.S. Army faces using Proton Exchange Membrane (PEM) fuel cells is reduced air flow for primary heat rejection in combat vehicles (due to a small operating space and the use of ballistic grills). Internal temperatures inside the stack increase to 140°C resulting in decreased performance. Additives to polymer membranes have been used to mitigate stack heat degradation but can contaminate and increase the electrical conductivity of the stack exhaust water. For water examined here which had a 0.7 mA current applied, an increase in electrical conductivity (using a 5vol% acetic acid mixture) promoted the platinum electrocatalyst detachment from the PEM fuel cell polymer membrane. The increased water conductivity resulted in 30-40% of the total platinum being detached within 67 minutes (400 current cycles).