Investigation of PEM Electrolyzer Performance with a Water-Fed Cathode

• Nicholas Hackett, Mechanical Engineering, University of Delaware
• Sergio Herrera, Mechanical Engineering, University of Delaware

• Ajay Prasad, Department of Mechanical Engineering, University of Delaware

Water electrolysis powered by renewable electricity is a promising pathway for sustainable hydrogen production. Typically, water is fed to the anode of a polymer electrolyte membrane electrolyzer (PEMEL). The PEMEL splits water to release oxygen at the anode and hydrogen at the cathode. Under normal operating conditions, a fraction of the hydrogen produced at the cathode crosses through the polymer membrane to the anode. When the hydrogen concentration in the oxygen stream reaches 4%, the mixture becomes potentially explosive, raising safety concerns. To address this issue, the Norwegian company, Hystar, has patented an approach that involves feeding water to the cathode and humidified air to the cathode. Diluting the crossed over hydrogen with air prevents its concentration from reaching the explosive limit. Our research focuses on testing Hystar’s claims and studying the impact of this cathode-fed setup on cell performance. Experiments were performed with membranes of different thicknesses and PEMEL performance was monitored as a function of flowrate of the anode humidified air stream. Preliminary results with the Nafion 115 membrane (127 μm thick) indicate that the PEMEL’s performance experiences a sharp drop upon switching to the cathode-fed setup. The performance is also sensitive to the supplied air flow rate and noticeably decreases below 400 sccm as the rate of water diffusing from the cathode side is too low to keep the membrane hydrated. Tests are ongoing to evaluate the PEMEL’s performance with a thinner Nafion 212 membrane (50.8 μm thick). Future research will focus on measuring hydrogen crossover in pressurized cathode-fed cells.