Fabrication of catalyst coated membrane electrode assembly for water electrolyzer using decal method

Abstract

Proton Exchange Membrane Electrolyzer (PEMEL) is a device that uses electricity to split water into hydrogen and oxygen. It is a promising technology to produce hydrogen gas, which is considered a clean and renewable energy source. The catalyst coated membrane (CCM) method is simpler and more efficient than the indirect coating method involving a transfer after coating on the substrate. However, the direct deposition of catalyst onto the membrane could be complicated by the transfer rate of the membrane during the coating process. This transfer rate poses a challenge in achieving consistent and high-quality catalyst coatings on the membrane surface. Therefore, controlling and mitigating the transfer rate of the catalysts to the membrane is of crucial importance in the CCM method for the fabrication of high-quality membrane electrode assemblies (MEAs) used in proton exchange membrane electrolyzers. This study aims to manufacture and optimize a catalyst-coated membrane electrode assembly (CCM-MEA) for a laboratory-scale proton exchange membrane water electrolyzer (PEMWE) using the decal method to achieve the highest transfer rate of the catalyst and to study other parameters that may influence the MEAs efficiency and durability. In this study also investigates and tests the long-term performance and durability of the MEAs. The CCM-MEA was manufactured using Nafion 117 and Nafion 212 membranes of different sizes (5 cm2, 25 cm2 and 36 cm2) with IrO2 coating on the anode side and Pt/c on the cathode side. The CCM was prepared using the decal method and different transfer substrates were tried such as PTFE, Kepton and Teflon cloth. To facilitate the transfer, a thin ionomer layer was added on top of the catalysts and the sample was sandwiched between a folded piece of aluminium foil before the hot press stage. For the hot press condition, the temperature was 130 °C, the pressure was 700 psi, and the time was 5 minutes. After the hot press, cold peeling of the sample by leaving it to cool down for 3 minutes. The performance of the CCM-MEA was evaluated in terms of current density under different operating temperatures (room temperature, 30 °C, and 60 °C). The results showed that the 36 cm2 using Nafion 117 at 2.0 voltage had the best performance among all the sizes of membrane used. Additionally, it was found that the Teflon cloth had the best catalysts transfer rate of over 95% among other transfer substrates. The result of this study provides insight on the optimal design, the long-term performance, and durability of the MEAs for PEMWE.