Three-Dimensional Numerical Simulation of Catalyst Ink Droplet Impact on Moving Patterned Substrates Based on the Multi-relaxation Lattice Boltzmann Method

To optimize the fabrication process of a catalyst-coated membrane and enhance the performance for proton exchange membrane water electrolysis, a three-dimensional multicomponent multiphase pseudopotential model based on the multiple-relaxation-time lattice Boltzmann method (MRT-LBM) is developed to numerically simulate the impact of catalyst ink droplets on a moving substrate. The effects of substrate moving velocity, surface morphology, microstructure size, and initial droplet diameter on the spreading behavior are systematically investigated. Results reveal that the moving substrate can enhance the droplet spreading. However, an excessively high velocity of the substrate leads to liquid accumulation at the front region of microstructures, thereby attenuating the horizontal spreading capacity of the droplet. Furthermore, compared with the plane substrate, the steady-state contact area of the liquid film is larger on the patterned structure. A more uniform liquid film distribution is achieved by the conical array substrate owing to its smooth and continuous curved surfaces. Although an increased initial diameter of the droplet facilitates overcoming the pinning effect on the substrate and improves the spreading capability, an excessively large initial diameter results in a thicker liquid film in the central region. These findings provide new optimization strategies for ultrasonic spray coating in the preparation of high-performance membrane electrode assemblies for proton exchange membrane water electrolysis.