Anodized titania nanotube array microfluidic device for photocatalytic application: Experiment and simulation

Abstract

Microfluidic photocatalytic reactors have advantages over conventional bulk reactors such as large surface-area-to-volume ratio and high control of fluid flow. Although titania nanotubular arrays (TNA) have shown enhanced photocatalytic degradation compared to nanoparticle films in a batch reactor configuration, their application in a microfluidic format has yet to be explored. The photocatalytic performance of a microfluidic reactor with TNA catalyst was compared with the performance of microfluidic format with TiO2 nanoparticulate (commercial P25) catalyst. The microfluidic device was fabricated using non-cleanroom based soft lithography, making it suitable for economical large scale manufacturing. The photocatalytic performance was evaluated at different flow rates ranging from 25 to 200μL/min. The TNA microfluidic system demonstrated enhanced photocatalytic performance over microfluidic TiO2 nanoparticulate layers, especially at higher flow rates (50–200μL/min). For instance, 12μm long TNA was able to achieve 82% fractional conversion of 18mM methylene blue in comparison to 55% conversion in case of the TiO2 nanoparticulate layer at a flow rate of 200μL/min. A computational model of the microfluidic format was developed to evaluate the effect of diffusion coefficient and rate constant on the photocatalytic performance. The improved performance of the TNA photocatalyst over the nanoparticle film can be attributed to higher generation of oxidizing species.