The influence of the surface morphology of 3-dimensional electrodes on the electrocatalytic activity and selectivity and methods for its assessment

This dissertation advances fundamental understanding of electrocatalyst design by demonstrating that catalytic performance can be strategically controlled through multiscale engineering approaches that extend beyond traditional active-site optimization. While conventional catalyst development has primarily focused on atomic-scale modifications, this research reveals that macroscopic electrode geometry and catalyst-support interactions significantly influence reaction selectivity, activity, and mechanism in alkaline electrochemical systems. Through systematic investigations of nickel-based electrocatalysts in two complementary studies, this work establishes new design principles for efficient, selective electrocatalysts for sustainable energy conversion and biomass valorization. The first research component examines how support materials influence the intrinsic activity and reaction mechanism of lanthanum cobalt oxide (LaCoO 3 ) perovskite catalysts for the oxygen evolution reaction (OER). Four support materials (nickel, iridium, platinum, and glassy carbon) were systematically investigated using comprehensive electrochemical techniques, including in situ Fourier-transform infrared spectroscopy, in situ Raman spectroscopy, and Mott-Schottky analysis. The results revealed that support materials significantly influence catalyst performance, with substantial differences in overpotential, charge-transfer resistance, and acceptor concentration observed across supports. Notably, X-ray photoelectron spectroscopy showed significant changes in cobalt oxidation states and surface oxygen species, particularly on nickel supports, suggesting that the OER may proceed via a lattice-oxygen mechanism on certain substrates. In situ FTIR further revealed changes in *–OH adsorption and interfacial water structure, providing evidence for support-induced shifts in the OER mechanism. The second research component investigates how macroscopic electrode geometry influences product selectivity in glycerol electrooxidation, a promising approach for valorizing biodiesel byproducts into value-added chemicals. Six additively manufactured nickel electrodes with systematically varied geometries (flat, dimple, small grid, medium grid, large grid, and cavity) were fabricated using laser powder bed fusion and comprehensively characterized. Remarkably, electrode geometry was shown to control product distribution, with the large-grid electrode achieving up to 95% selectivity for formic acid and the highest glycerol conversion of 28.3% with 99% carbon balance. The introduction of the surface area at zero depth (SA(0)) concept provided quantitative insights into the relationship between geometric structure and selectivity, revealing that deeper cavities and confined structures promote enhanced oxidation to C1 products by restricting the diffusion of C2 and C3 intermediates. These findings demonstrate that electrode architecture can be strategically designed to control reaction pathways and enhance selectivity. Collectively, these two studies demonstrate that electrocatalyst design must consider structural and interfacial effects across multiple length scales. The work establishes strategic control over macroscopic geometry and catalyst-support interactions. These insights contribute to the rational design of electrocatalysts for sustainable energy applications, including biomass valorization and water-splitting technologies, which are essential to the transition to a renewable energy economy.