Pure Hydrogen/Oxygen Fuel Cell Performance Assessment for Closed-Loop Renewable Energy Systems

Fuel cells and electrolysis are promising candidates for future energy production from renewable energy sources. Usually today's fuel cell systems run on hydrogen and air, while electrolysis systems vent out oxygen as a by-product. 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 the MEA which showed the optimum under pure H2/O2 operation starting from a preliminary experimental characterisation of three commercial MEAs (IRD XL PFSA reinforced membrane, Baltic with Nafion 212 membrane and a Alfa-Aesar PFSA), tested using pure hydrogen and oxygen under different RH (dry-25-50-75-100%) and pressure (1-3-5 absolute bar) conditions. Critical aspects, such as membrane failure, limit operative conditions and system design have been discussed along with experimental analysis. The results showed that: - The best performance have been obtained from Alfa-Aesar MEA at higher RH, meanwhile operation/testing below 25% RH always led to membrane failure. - Higher pressure increase performance in all RH conditions, but its influence is more evident at low RH. - Despite the higher performance, high pressure and temperature combined effects often lead to membrane failure which make this operation mode very critical. The most reliable operative conditions have been obtained at 3 bar (abs.) and high RH value (>50%), resulting in stable and reliable operation for all the tested MEAs, while low RH operation leads easily to membrane failures. Under these conditions IRD reinforced membrane MEA has shown a high reliability in all conditions, although featuring lower performances mainly due to high membrane Ohmic resistance. caused by the presence of the reinforcement. Beside, the experimental activity has shown the critical aspects to be considered for closed-loop fuel cell systems operating with pure hydrogen and oxygen.