Pressurized Water Electrolysis Using Hydrophobic Gas Diffusion Layer with a New Electrolyzer Cell Structure

Abstract

Direct production of pressurized hydrogen through polymer exchange membrane (PEM) water electrolysis without the usage of the external compressor is an industrially important approach to maximize energy efficiency. An additional challenge in conventional water electrolyzers is the separation of the generated gases, hydrogen and oxygen, from water. In this report, we demonstrate the operation of a new water electrolysis cell at high inlet water pressure with the assistance of a hydrophobic gas diffusion layer (hydrophobic-GDL). This configuration allows us the gas/water separation taking place at the electrode so that pressurized water-free gases can be the output. The membrane electrode assemblies (MEAs) were prepared using the hydrophobic-GDL, a Nafion membrane, and Pt-C/IrO2 catalysts. Electrolysis experiments were performed at different temperatures with pressurized water (ΔP = 0.05 – 0.4 MPa based on atmospheric pressure) resulting output was pressurized (0.05 – 0.4 MPa) hydrogen and oxygen gases. The current densities at 1.6 V of electrolysis voltage were 117, 188, 262 mA cm-2 at 25, 60, and 80oC, respectively, and the hydrogen and oxygen gas evolution rates were consistent with theoretical values. It was found that increasing water pressure is beneficial to the electrode kinetics and the increase in water transport to the electrode surface as well as efficient gas separation and the production of pressurized gases.

Keywords: Water pressure, hydrophobic gas diffusion layer, PEM water electrolysis, hydrogen production