Two-dimensional model of low-pressure PEM electrolyser: Two-phase flow regime, electrochemical modelling and experimental validation

Abstract

Based on proton conduction of polymeric electrolyte membrane (PEM) technology, the Polymer Electrolyte Membrane Water Electrolyser (PEMWE) offers an interesting solution for efficient hydrogen production. During the electrolysis of water in PEMWE, water is split into oxygen, protons and electrons at the anode and a water-gas two-phase flow results. The aim of this study is to investigate the link between the two-phase flow at the anode side and cell performance under low-pressure conditions. We have developed a two-dimensional stationary PEMWE model that takes into account electrochemical reaction, heat transfer, mass transfer (bubble flow) and charge balance through the Membrane Electrodes Assembly (MEA). In order to take into account the changing electrical behaviour, our model combines two scales of descriptions: at microscale within anodic active layer and MEA scale. The water management at both scales is strongly linked to the Not Coalesced Bubble regime (NCB regime) or the Coalesced Bubble regime (CB regime). Therefore, water content close to active surface areas depends on two-phase flow regimes. Our simulation results demonstrate that the coalesced phenomenon is associated with improvement of mass transfer, a decrease in ohmic resistance and an enhancement of the PEMWE efficiency. At low and medium current density values, the model has been validated using two separate experiment electrolysis cells.