Date of Award

Spring 2026

Document Type

Open Access Thesis

Department

Chemical Engineering

First Advisor

Sirivatch Shimpalee

Abstract

Direct seawater electrolysis (DSE) has gained increasing attention as a sustainable method for hydrogen production that does not require purified water resources. The ionic composition of seawater, especially the concentrations of sodium (Na+) and chloride (Cl-) ions, plays a critical role in determining the electrochemical behavior, membrane transport properties, and overall system performance. This thesis presents a numerical investigation of a model direct seawater electrolyzer with a focus on understanding how changes in seawater ionic strength influence device operation.

A three-dimensional multiphysics Computational Fluid Dynamics (CFD) model was developed in STAR-CCM+ to simultaneously solve heat and mass transport, charge transport, ionic conduction, and electrode reaction kinetics. Several membrane conductivity correlations were formulated to represent different theoretical descriptions of how Na+ and Cl- ions affect proton transport through the membrane. These correlations were incorporated into the numerical framework to evaluate their impact on cell voltage, overpotential distributions, and hydrogen generation rates.

Simulations were performed at operating temperatures of 323 K, 353 K, and 368 K and for seawater ionic concentrations of 0.2 M, 0.5 M, and 1.0 M for Na+ and Cl-. The results show that moderate increases in ionic concentration enhance electrolyte conductivity and reduce ohmic losses, while higher concentrations intensify polarization effects and promote competing reactions. Temperature was found to significantly improve ionic mobility and membrane conductivity, resulting in lower cell voltages and improved performance under all operating conditions examined.

Overall, the findings of this study highlight the complex interaction between seawater composition, membrane transport behavior, and electrochemical processes. The insights gained from this modeling work provide a quantitative basis for optimizing membrane properties and operating strategies in future direct seawater electrolysis systems for efficient hydrogen production.

Rights

© 2026, Fethi Mustafa Cimen

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