Measurement of water permeation through membranes from extremely high hydraulic pressure to atmospheric pressure

Abstract

The performance of electrochemical hydrogen compressors (EHCs) with polymer electrolyte membranes which work in the presence of water is affected by the flooding; however, the water permeation through the membranes from the high-pressure side (dozens of MPa) to the low-pressure side has never measured. In this study, a method to measure the permeation from the high hydraulic pressure side (2–20 MPa) to the atmospheric pressure side is shown, using EHC cells and a water hydraulic pump. By this method, liquid-liquid permeation (LLP) and liquid-vapor permeation (LVP) were measured. The higher the hydraulic pressure was, the more the water flux was, and the increase in the permeation was large for LLP. It is considered that the electro-osmotic drag accumulates water on the cathode at low pressure during the initial stage of the electrochemical hydrogen compression and then the permeation from the cathode to the anode exceeds the electro-osmotic drag as the cathode pressure increases, which causes the decrease in the performance by flooding.