LBM studies on oxygen bubble transport in porous transport layers and flow channel of proton exchange membrane water electrolyzers

The transport and management of oxygen bubbles significantly impact the performance of proton exchange membrane water electrolyzers (PEMWE). The 3D structures of sintered and fibrous porous transport layers (PTLs) were reconstructed using randomly distributed spherical particles and layer-by-layer generated cylindrical fibers, respectively. The two-phase flow dynamic behavior of oxygen in the PTL and flow channel with lateral velocity were simulated based on the lattice Boltzmann method with a free surface model. At the bottom of the computational domain, spherical bubbles were added at random positions at specified intervals, corresponding to different current densities. The effects of bubble generation time interval, contact angle, initial flow velocity, graded porosity and microporous layer structure are investigated. The similarities and differences between spherical and fibrous PTLs are analyzed in detail. The results demonstrate the feasibility and necessity of operating PEMWEs at high current densities. Hydrophilic PTLs facilitate the upward movement of oxygen bubbles, with an optimal contact angle range observed. Maximizing the flow channel velocity within laminar conditions promotes the lateral expulsion of bubbles. Compared to spherical PTLs, fibrous PTLs are more suitable for high current density operations. Reducing the porosity or decreasing the fiber diameter near the catalyst layer side can effectively minimize bubble accumulation. • A 3D lattice Boltzmann model with free surface model is developed. • A random bubble generation model is constructed to link with electrochemistry. • The dynamic bubble evolution in the PTLs and flow channel is studied. • The differences caused by spherical and fibrous PTLs are investigated. • Different PTL properties are studied to understand oxygen transport.