Pore-scale simulation of oxygen transport in a proton exchange membrane electrolysis cell: Effect of the hydrophilia of porous transport layer and catalytic layer

Proton exchange membrane water electrolysis (PEMWE) shows great potential in coupling fluctuating renewable energy for hydrogen production. In PEMWE, the counter-current transport of oxygen in the porous transport layer (PTL) limits the process of water reaching the catalyst layer (CL), significantly affecting the performance and stability of PEMWE. Herein, a lattice Boltzmann model coupled with a reaction boundary is proposed to consider the mechanism of oxygen expelling due to increased pressure. The model is adopted to study the influence of PTL and CL hydrophilia on the mechanism and pattern of oxygen transport. The results suggest that the PTL hydrophilia results in three different flow patterns before the oxygen breakthrough occurs. After the oxygen breakthrough, the extent of oxygen retreatment is also affected by PTL hydrophilia. Increasing PTL hydrophilia can reduce the oxygen saturation within the PTL, but may increase the saturation on the CL surface. A significant decrease in oxygen saturation at the CL surface can be achieved by increasing the hydrophilia of the CL, and even a minor increase in hydrophilia from 74.5 to 54.9 can lead to a reduction of up to 50 % in oxygen saturation. These findings have implications for rationally designing PTL structures.