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

Highlights: • UV-irradiated fluidized bed photocatalytic system was applied to water splitting. • The parasitic Pt-catalysed back reaction can be reduced through novel designs. • A model describing the performance was developed and validated experimentally. • The model can be applied to the optimization of photocatalytic systems. 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 H₂ and O₂. 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 H₂ and O₂, 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.