A component-level model of polymer electrolyte membrane electrolysis cells for hydrogen production

Abstract

Proton Exchange Membrane Electrolysis Cells (PEMEC) are a promising technology for high-purity hydrogen production with a low impact on the environment. This paper developed a component-level PEMEC model, which considers the water exchange between the anode and cathode, two-phase transport in the porous transport layer (PTL), flow resistance at the PTL/Channel interface, gas coverage at the catalyst surface, proton conductance in the membrane, and electrochemical reaction kinetics. An interfacial resistance for oxygen removal at the anode Channel/PTL interface is proposed for the first time, which is based on the well-known mass convective transport theory. A gas coverage sub-model on the catalyst surface and 1-D liquid transport sub-model in the anode PTL are incorporated into the PEMEC model. The model is validated against various sets of experimental data reported in the literature. Results show that the ohmic overpotential contributes to a major voltage loss (about 52%) and the activation overpotential contributes approximately 38% at 5 A/cm2. The mass transport loss increases with the current density, accounting for about 10% at 5 A/cm2 to 18% at 7 A/cm2 under a gas coverage coefficient of 2.0, and about 25% at 7 A/cm2 under a larger gas coverage coefficient of 3.0. Additionally, at a high current density of 5 A/cm2 the oxygen fraction at the PTL may occupy as large as 55% in the pore space, hampering liquid water supply to the catalyst layer and increasing the transport loss. The model is suitable for rapid design and optimization of PEMEC components and operation conditions and integration with renewable resources such as solar or wind energy.