Koel, Bruce EdwardBoniface, Kenny2025-08-122025-08-122025-05-20https://theses-dissertations.princeton.edu/handle/88435/dsp01mg74qq58rThis thesis investigates electrolytically driven calcium carbonate precipitation as a pathway for carbon dioxide mineralization through induced alkalization. Using a three-electrode setup with nickel foil as the working electrode, electrolysis of potassium bicarbonate solutions was conducted at controlled current densities to generate hydroxide ions via the hydrogen evolution reaction (HER). In-situ Raman spectroscopy was used to monitor interfacial speciation and quantify local pH near the electrode surface. Starting from an open-circuit pH of 8.35, the pH rose to 9.42 at two minutes and reached 10.83 after six minutes of electrolysis at −2 mA/cm2. Calcium carbonate precipitation experiments were conducted using solutions of sodium chloride and calcium chloride mimicking seawater concentrations. A key finding was that precipitation occurred primarily in the bulk of the solution, rather than directly at the electrode surface. This was confirmed by visual observations during electrolysis and supported by electrochemical impedance spectroscopy (EIS) measurements. While charge transfer resistance (Rct) remained high throughout, the relatively stable solution resistance (Rs) and increasing Warburg impedance over time indicated minimal surface blockage and a dominant role of diffusion-driven precipitation in solution. To further understand the precipitation process, Raman spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDXS) were used to characterize the solid calcium carbonate products. The predominant polymorphs identified were calcite and vaterite. SEM images showed that the crystals had well-defined morphologies, with spherical vaterite and rhombohedral calcite observed. Taken together, these results demonstrate the effectiveness of electrolytically driven alkalization for inducing carbonate formation and provide mechanistic insight into spatial precipitation behavior. The findings offer valuable direction for optimizing electrode and cell design in future electrochemical carbon capture systems.en-USPrinceton University Senior Theses