PhD Oral Exam - Camilo Perdomo, Chemical Engineering

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Conventional wet-chemical synthesis routes for heterogeneous catalysts carry significant environmental footprints due to intensive solvent and energy consumption. This dissertation demonstrates Resonant Acoustic Mixing (RAM) as a rapid, solvent-minimized alternative to traditional precipitation and deposition processes. To establish the synthesis conditions and parameters that lead to photocatalytically active materials, TiO2-supported Co, Cu and Ni co-catalyst heterostructures and bulk NiAl-, NiFe-, and CoAl- layered double hydroxides (LDHs), were investigated as model catalytic systems.

The role of parameters such as vibrational acceleration, liquid-to-solid ratio, mixing times, reaction kinetics, and precursors mixture composition on the properties and photocatalytic H2 evolution and CO2 reduction performance of the prepared samples was systematically evaluated. High fluidization dynamics achieved with acoustic mixing in RAM, under low liquid-to-solid ratio (~0.3 µL liquid/mg solid precursor) and moderate RAM accelerations (30 g) yielded efficient precursor dispersion and intimate metal-semiconductor interfacial contact without liquid-phase or milling media, as well as excellent phase purity. Advanced structural and optical characterization (including PL, XPS, and HR-TEM) revealed that RAM processing outperforms conventional wet-chemical approaches in enhancing the physicochemical properties, driving improved optical response and charge carrier dynamics that translate into higher photocatalytic activity compared to analogous control samples.

The elimination of bulk solvents during the synthesis stage, and the removal of unnecessary washing steps drastically reduce liquid effluent generation and energy consumption in this RAM-assisted methodology. Consequently, this work establishes Resonant Acoustic Mixing as a robust and greener alternative to conventional wet-chemical routes for manufacturing advanced functional materials.