Development of advanced porous transport electrodes for water electrolysis

“Green hydrogen” is expected to play a pivotal role in decarbonizing various industrial sectors, including transportation, metal production, and chemical processes. However, as of 2024, the relatively high cost of green hydrogen ($5–$7 per kilogram) remains the primary barrier to its large-scale commercialization. Reducing its price significantly depends on lowering capital costs and enhancing the performance of green hydrogen generators, specifically proton exchange membrane water electrolyzer cells (PEMECs). My dissertation addresses the cost and performance challenges of PEMECs by investigating mass transport phenomena and developing advanced porous transport electrodes.

This dissertation starts with the mechanism investigation of mass transport in PEMECs. With the help of a high-speed and micro-scale visualization system (HMVS), the bubble dynamics in various PTLs and operation conditions were clearly captured and analyzed. It is found that the PTL structure and bubble release efficiency have a significant dependance. PTLs with relatively large and low-tortuosity pores benefit the bubble release. Notably, the bubble release efficiency is changeable depending on the evolution of catalyst surface during the operation. More importantly, an interface-visible characterization cell (IVCC) was successfully developed, which can directly observe the mass transport in the electrode/electrolyte interface for the first time. The local bubble blockage and dehydration were unveiled for the first time. To understand the observed phenomena, a 3D multiphysics model was developed. It is found that the local bubble blockage and electrode pattern will cause significant local current crowding and dehydration, which degrades the performance of PEMECs. Based on these discoveries, the flow-enhanced liquid/gas diffusion layer (FELGDL) and reaction enhanced liquid/gas diffusion layer (RELGDL) were successfully developed, and their advances were successfully demonstrated in PEMECs. Finally, the integration methods between catalyst layers and porous transport layers are investigated. A novel electrodeposition-based ink-free integrated dual electrode assembly (IDEA) is developed serving as high-performing and durable electrode assembly for “green hydrogen” production. We believe the comprehensive mechanism investigation, numerical analysis, and innovative design/manufacturing approaches developed in this dissertation can serve as a guideline for the next-generation electrodes for affordable “green hydrogen” production.