Effectiveness of Gas Recombination Catalyst Layers in Mitigating H2 Crossover in PEM Water Electrolyzers Operating at High Differential Pressure

Abstract

Gigawatt-scale deployment of proton exchange membrane water electrolyzers (PEMWE) to produce green hydrogen at $1/kg of H2, the US department of energy’s (DOE) ultimate cost target, requires the use of thinner membranes to reduce ohmic losses at high current densities as well as differential pressure operation to improve the overall system efficiency.1 High differential pressure operation results in significant hydrogen crossover through PEMs leading to safety concerns due to the formation of a flammable gas mixtures at anode (> 4% H2 in O2).2 Therefore, the successful deployment of PEMWEs at scale relies on successful implementation strategies to reduce the hydrogen concentration at anode to enable safe operation at high efficiency. These strategies include incorporating gas recombination catalyst (GRC) in the membrane, PTL or downstream in the anode gas outlet. However, the impact of GRC layers on PEMWE performance and hydrogen crossover rates at high differential pressure is not well understood.In this work, we employ in-operando gas chromatography coupled with thermal conductivity detector along with PEMWEs operating at differential pressures (up to 30 bar) to quantify hydrogen crossover rates through PEM at differential pressure. Using this setup, we evaluate the effectiveness of gas recombination layers incorporated in PEMWE membrane electrode assemblies (MEA) in mitigating the risk of formation of the flammable gas mixture. Further, we will also discuss implications of high differential pressure operation on PEMWE performance, durability, and operational safety.