High Pressure Water Electrolysis Using a Hydrophobic Gas Diffusion Layer with a New Cell Structure of Water Absorbing Electrolyte Cell

Abstract

Nowadays, the usage of fossil fuel has been raised as a non-sustainable resource, account for the main contributor to global warming (CO2 emission) and environmental pollutions. In this regard, the hydrogen production through polymer electrolyte membrane (PEM) water electrolysis is an industrially important approach to resolving the above energy issues. Precious metals are the top metal-catalysts that can offer to generate hydrogen efficiently and earth-abundant nonprecious metal catalyst has large overpotential issues because of a low electro-activity. Therefore, the 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. Because hydrogen is believed to be a clean energy carrier to store the excess renewable energy to resolve its intermittent issues. Although over 96% of the current hydrogen produced is via the reformation of natural gas and the remaining 4% produced from water electrolysis and it is the “green” approach to produce hydrogen without CO2 emission. In this report, we demonstrated the operation of a new water electrolysis cell at high water support pressure with the assistance of a hydrophobic gas diffusion layer (H-GDL) and demonstrated a high-pressure PEM water electrolysis experiment with the assistance of a newly structured water electrolysis cell (Fig.1a). The membrane electrode assemblies (MEAs) was prepared using H-GDL, membrane, Pt-C//IrO2 and the electrolysis experiment was performed at different temperature and water support pressure (ΔP = 0.05-0.4 MPa). The current density obtained at 1.6 V were 117, 188, 262 mA cm-2 at 25, 60, and 80oC (Fig.1b), respectively, and the generated gas evolution rates (hydrogen and oxygen) were consistent with theoretical value with efficiencies up to 87%. It was found that increasing water pressure is beneficial to the electrode kinetics and mass-transportation due to an increase in water transport to the electrode surface and efficient gas separation. The benefits of using GDL is, therefore, lying on two points. Firstly, high pressure can be applied to the water, which allows the operation of the cell at a temperature higher than 100℃, while maintaining the water in the liquid phase and secondly the high-pressure operation using H-GDL is the production of pressurized hydrogen gas without the use of an external compressor. As advantages, in the future, it can be directly used to fuel cell and that can be stored in a hydrogen tank without further purification process. Figure 1