UBC Theses and Dissertations
Photocatalytic hydrogen production in a UV-irradiated fluidized bed reactor Reilly, Kevin
Growing global energy demands and an increased environmental awareness have resulted in a demand for renewable energy sources. Photocatalytic water splitting has long been explored as a direct solar-to-chemical energy conversion method in the hopes of creating a sustainable, emissions-free hydrogen production process. In this thesis we present the first focused effort on hydrogen production via photocatalytic water splitting in a UV-irradiated fluidized bed reactor. This novel approach was taken to address the mass-transfer effects, poor radiation distribution, parasitic back-reaction and photocatalyst handling difficulties that limit the efficiency and scalability of existing water splitting systems. By fluidizing platinum-deposited TiO₂ spheres in a 2.2M Na₂CO₃ solution, steady hydrogen production rates of 211 μmol/hr with an apparent quantum efficiency of 1.33% were achieved upon UV-irradiation. This represents a marked 44% increase in efficiency when compared to results obtained by suspended slurry TiO2 photocatalysts in the same reactor. A mathematical model describing the performance of the fluidized bed water splitting system was derived and then employed to estimate several key parameters. From the model, it was found that high rates of mass transfer in the separator unit could minimize the negative effects of the parasitic back reaction and greatly improve the overall rate of hydrogen evolution. Indeed, it was demonstrated experimentally that slight modifications to the liquid-gas separator to improve mass transfer resulted in a 350% increase in the rate of hydrogen evolution. The application of the model to the design of fluidized bed water splitting systems is described. Advanced, fluidizable nanowire and nanorod photocatalysts that can withstand the rigors of fluidization are described here for the first time. We present two novel, scalable methods that allow for the growth of anatase nanowires or rutile nanorods on porous glass particles, whose deep surface features protect the nanostructured films from mechanical attrition. It was found that the photocatalytic activity of anatase nanowires grown via a chemical bath deposition process was over three times greater than that of hydrothermally grown rutile nanorods when employed for photocatalytic hydrogen production and degradation of a model contaminant (Rhodamine B). The factors controlling nanowire growth and performance are discussed.
Item Citations and Data
Attribution-NonCommercial-NoDerivatives 4.0 International