INVESTIGATION OF PURE HYDROGEN/OXYGEN PEFC

A typical Polymer Electrolyte Fuel Cell (PEFC) combines hydrogen from a tank and oxygen from the air to produce electricity, leaving water and heat as its only byproducts, while electrolysis systems vent out oxygen as a by-product. In this last case, the decision on whether to store oxygen or vent it strongly depends on application. Systems that use oxygen may totally be closed to the environment, which is critical in applications where maintenance is difficult or costly, but for space applications, oxygen storage is the only option. In other words, instead of using oxygen from the air like other regenerative fuel cells, the closed-loop system re-uses the oxygen extracted from the water. That makes it ideal for use on the moon, where there is no oxygen. Replacing air with pure oxygen, fuel cell electrochemical performance, durability and system efficiency can be significantly increased, with a further overall system simplification and increased reliability. This work, which represent the initial step for pure H2/O2 fuel cell operation in closed-loop systems, focuses on performance validation of a cell operating under pure H2/O2 conditions, different relative humidity (RH), reactant stoichiometry conditions and cell temperature. Critical aspects, such as membrane failure, limit operative conditions and system design have been discussed along with experimental analysis.