Lattice Boltzmann method modeling and experimental study on liquid water characteristics in the gas diffusion layer of proton exchange membrane fuel cells

Abstract

Water transport through the gas diffusion layer (GDL) is vital to proton exchange membrane fuel cells (PEMFCs), especially under flooding conditions. In this paper, a two-dimensional (2D) lattice Boltzmann method (LBM) is applied to reveal the water dynamic characteristics in GDL, and the computational domain is reconstructed based on the experiment. In-situ experiments, including I–V performance and electrochemical impedance spectroscopy (EIS) tests under flooding conditions, are carried out and analyzed. It is found that the porosity distribution inside the GDL is a crucial factor in water dynamic behavior research. The horizontal liquid water saturation (HSw) under the channel of real GDL (with porosity distribution) at 0.4 relative thickness are 3.2 times, 2.1 times and 3.4 times higher than the ideal GDL (without porosity distribution) in the case of 0.8 mm, 1.2 mm and 2.0 mm, respectively. The numerical simulation and experimental study show that water dynamic characteristics under the rib influence cell performance directly. In our LBM model, the GDL water distribution inconsistency (Varw) under 2.0 mm width rib is 43.1% and 28.0% higher than that under the 0.8 mm and 1.2 mm rib, respectively. With the rib wider from 0.8 mm to 2.0 mm, some parts of cell impedance such as Rmt, Rct, and Lmt increase 64.22%, 98.89%, and 47.46%, respectively. However, GDL under the channel shows no influence on water transport process.