On the Catalytic Degradation in Fuel Cell Power Supplies for LongLife Mobile Field Sensors

Networks of sensor modules operating in unstructured outdoor environments have many important applications including environment monitoring in forestry, agriculture, disaster prediction (storm, earthquakes, tsunamis), energy (exploration, transportation, consumption) and border security [29]. These field sensor modules may be required to operate unattended for 3–5 years or more with only onboard power. Currently, such field devices use batteries or photovoltaics for power. Photovoltaics are not used often because they require large surface areas with good exposure to the sun [26]. As a result, batteries are most commonly used to power field systems. However, their lives are often limited by the total energy they can provide. Conventional batteries provide high and variable power, but their total energy is limited due to their internal chemistry. For long life missions, they need to be recharged or replaced often. While significant work is being done to address their energy limitations [25], batteries currently cannot meet the high energy requirements of many long duration field sensors. Here, fuel cells are explored to meet these requirements. Fuel cells have been suggested as a power source for field and mobile devices [32–35]. Fuel cells are electrochemical energy conversion devices that convert chemical energy directly into electricity. They can have high operating efficiencies and energy densities. In particular, proton exchange membrane (PEM) fuel cells are well suited for field devices, because of their high conversion efficiencies of 40–65% (LHV) [23, 24]. They operate at or near room temperature and produce clean exhaust. PEMs use hydrogen fuel and breathe oxygen to produce electricity [23, 24]. PEMs tend to have higher specific energy than the best current batteries. However, PEM fuel cells face several challenges that limit their wide scale commercial adoption. First, PEM fuel cells are faced with low durability, due to degradation of its components, resulting in short lives [3, 9, 13–15, 46]. Although significant research and progress has been made in this field