Water transport analysis during cathode dry operation of anion exchange membrane water electrolysis. (15th December 2022)

• Record Type: Journal Article
• Authors: Wang, Ruixiang; Ohashi, Masato; Ishida, Masayoshi; Ito, Hiroshi
• Is Part Of: International journal of hydrogen energy. Volume 47:Number 97(2022)
• Page Start: 40835
• Page End: 40848
• Publication Date: 2022-12-15
• Subjects: Anion exchange membrane -- Water electrolysis -- Concentration overpotential -- Dew point -- Water diffusion -- Cathode dry operation; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2022.09.181
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: The effect of water diffusion through an anion exchange membrane (AEM) on the concentration overpotential ( η conc ) during cathode dry operation of AEM water electrolysis was experimentally examined using electrolytic cells with different membrane electrode assemblies (MEAs). The specially designed MEAs were used in the cells to obtain reliable and reproducible data to clarify the influence of membrane thickness ( t mem ) and porosity of cathode catalyst layer (CL). The relative humidity of generated hydrogen ( ϕ H2 ) during electrolysis was also measured based on dew point measurements of the hydrogen. The η conc analysis for cells with single- and double-AEM MEAs revealed that water diffusion through the membrane was the main contributor to η conc . The quantitative agreement between ϕ H2 data and η conc revealed that the difference in η conc between the two types of MEAs is explained by the water concentration difference between anode and cathode via the Nernst equation. The effect of the porosity of the cathode CL on cell performance and on water transport was also examined experimentally. The results revealed that a high-porosity cathode CL tended to keep the cathode in a drier state during electrolysis compared with a low-porosity cathode CL. When ϕ H2 is lower than a threshold value in the range from 0.5 to 0.6, the ion conductivity of AEM and ionomer would decrease, and the cell performance would deteriorate due to an increase in cell resistance ( R cell ) and/or activation overpotential ( η act ). Graphical abstract: Image 1 Highlights: Effect of water diffusion on the concentration overpotential was examined. Specially designed MEAs were used to obtain reliable and reproducible data. Water diffusion was the main contributor to concentration overpotential. A high-porosity cathode CL tended to keep the cathode in a drier state.