Model-guided intensification of photocatalytic reactions in a parallel-plate microfluidic reactor with immobilized TiO2

• Parallel-plate microfluidics enables intensified TiO₂ photocatalysis under flow. • Robust spin-coated TiO₂ films retain activity in batch and microreactor systems. • Microfluidic operation delivers higher space–time yields than batch reactors. • Model-based analysis links transport, photon input, and surface kinetics. • A transferable framework for designing intensified photocatalytic microreactors. We report the development of immobilized TiO₂ photocatalyst films integrated into a transparent microfluidic reactor for hydroxyl-radical-based advanced oxidation. Spin-coated TiO₂ films using a TEOS binder were homogeneous, mechanically robust, and retained anatase crystallinity and optoelectronic properties. Structural and chemical characterization (FTIR, XRD, SEM-EDX, profilometry, CHNS) confirmed Ti–O–Si linkages, uniform elemental distribution, and UV-induced surface reorganization accompanied by increased roughness. Photocatalytic activity was evaluated using coumarin as a fluorescent probe to comparatively assess • OH-related activity. The films exhibited reproducible radical generation after UV preconditioning, while prolonged irradiation caused only minor surface deactivation. In a parallel-plate microfluidic reactor, significantly higher 7-hydroxycoumarin formation was achieved compared to batch operation, reflecting pronounced process intensification. The microfluidic system exhibited substantially improved photon utilization (approximately sixfold higher apparent quantum yield) and nearly three orders of magnitude higher volumetric productivity, demonstrating more efficient coupling between photon absorption, mass transport, and surface reaction under continuous-flow conditions. A two-dimensional convection–diffusion model with pseudo-first-order surface kinetics reproduced experimental trends and enabled estimation of apparent surface rate constants. Simulated concentration fields revealed operation in a photon- and surface-kinetics-controlled regime under the applied conditions. Overall, this work establishes a model-guided framework combining reproducible catalyst immobilization, quantitatively demonstrated microfluidic process intensification, and predictive analysis to support rational reactor design and the development of intensified photocatalytic systems.