Multiphase Fluid Dynamics and Mass Transport Modeling in a Porous Electrode toward Hydrogen Evolution Reaction

The intrinsic activity of hydrogen evolution reaction (HER) catalysts has been significantly improved in the past decades, and current efforts are devoted to implement these catalysts for HER applications through electrode design and fabrication. However, HER in an electrode usually involves complex processes including electrochemical reaction, ion transport, bubble behavior, and gas-liquid flow near the electrode surface. The coupling of different processes makes it difficult to accurately analyze the effect of each process on the HER performance of the electrode. In this paper, a multiphase fluid dynamics and mass transport model is proposed to decouple the HER processes and provide a deep understanding on the interactions among those processes. The results reveal a strong interaction between ion transport inside the electrode and bubble detachment/ascending outside the electrode. The surface design can effectively improve the velocity profile of the liquid and hence dominate the ion transport near the electrode, whereas the design of pore structure can remarkably enhance the ions diffusion inside the electrode. In addition, external forced electrolyte flow can further enhance the fluid convection and ion transport when the speed of forced flow is higher than that induced by bubble ascending. These results conclude that the proposed model contributes to the understanding of interactions among electrochemical reaction, ion transport, bubble behavior, and gas-liquid flow near the electrode surface, providing a guideline for HER electrode design.