Photocatalytic water splitting in a fluidized bed system: Computational modeling and experimental studies

Photocatalytic water splitting in a novel, UV-irradiated fluidized bed reactor system with Pt-deposited titanium dioxide (TiO2) particles has been explored as an alternative approach to hydrogen production. A model describing the water splitting performance of the fluidized bed system was developed through a holistic approach combining fluidized bed theory, mass transfer effects, an optical model, and a proposed mechanism for the parasitic Pt-catalysed back reaction of H-2 and O-2. The model was validated experimentally using fluidizable Pt-deposited TiO2 particles. It was found that the efficiency of the fluidized bed water splitting system is dependent on the rate of mass transfer in the gas-liquid separator, while the overall rate of hydrogen evolution was found to vary with the height and density of the photocatalyst bed in the reactor; all of which are functions of the fluidization flow rate. It is shown that maximizing the rate of mass transfer in the gas-liquid separator can greatly diminish losses due to the Pt-catalysed back reaction of H-2 and O-2, yielding significant gains in efficiency and the overall rate of hydrogen production. The application of the model to the design of the fluidized bed water splitting system, the sub-systems and the photocatalyst particles is discussed.