UC Irvine

Water electrolysis makes it possible to electrochemically split water to produce hydrogen, a popular solution for the current global challenges related to climate change. Polymer electrolyte membrane electrolysis cells (PEMECs) are one of the most popular types of electrolysis cells due to their high efficiencies (60-90%), low operating temperatures (e.g., 20-100°C), and high operating current densities (e.g., >5 A/cm2) desired to increase the gas production rate, but this may cause gas accumulation in the reaction, which reduces the surface area for the desired electrochemical reaction. In comparison with PEMECs, solid oxide electrolysis cells (SOECs) operate at higher temperatures (e.g., 700°C-1,000°C), reducing the electrical energy required for the process since part of it is replaced by heat and increasing its efficiency (e.g., > 100%). These types of cells require good thermal management along with the best combination of operating conditions to ensure a minimum electrical requirement and heat addition/removal. Mathematical modeling serves as a powerful tool in water electrolysis to study complex phenomena occurring within the cells. By mathematically representing the physical and chemical processes involved, models provide insights into the intricate interplay between various factors such as fluid dynamics, electrochemical reactions, and mass/heat transfer. This technique offers a cost-effective and time-efficient way of exploring different operating conditions and design parameters, allowing for virtual experimentation and optimization before physical prototypes are constructed. This dissertation focuses on advancing the understanding of PEM and solid oxide water electrolysis through a comprehensive component-level modeling framework, which can be extended to simulate SOECs as the basic principles of electrochemistry and transport phenomena remain applicable. The main framework considers a Butler-Volmer approach, Nernst equation, homogeneous properties within the individual components of the cell, interfacial transport resistance, activation, and ohmic losses. For the PEMEC portion, the considerations for liquid water transport and gas coverage on the catalyst surface are introduced, including an innovative interfacial model for oxygen removal at the anode PTL interface to enhance the predictive accuracy. On the other hand, the SOEC adaptation introduced a thermal model by incorporating the effects of heat transfer mechanisms. Both models were validated against experimental data to later explore the impact of different operating temperature, pressure, geometry, and material properties on the performance of the cells. This modeling framework enables us to investigate at multiple scales the behavior of these technologies, driving efficiency improvements and cost reduction in hydrogen production processes.