UT-3 thermochemical hydrogen production cycle has been studied, both theoretically and experimentally, and is one of the very few cycles studied on a pilot plant scale. The maximum operating temperature in this cycle is relatively lower than the temperatures in other cycles. Another advantage of this cycle is that it is comprised of four gas-solid reactions which simplify product separation. Although the cycle has several such advantages, one of the significant issues is the development of solid reactants that are chemically reactive and physically stable in cyclic operations between oxide and bromide forms, which have considerably different molar volumes. Acceleration of reaction rate as well as longer cyclic life time and durability of the solid reactant are important keys for the practicability of the cycle. Additionally, a simpler preparation step of the reactant is preferable. Therefore, in order to increase the surface area of the calcium oxide reactant and maintain reactivity as well as structure in cyclic transformations, porous calcium oxide films have been examined as candidates. The calcium oxide precursor was prepared by sol-gel chemistry following a metal alkoxide process and the film was fabricated by a dip coating procedure. The characterization of the calcium oxide film such as the structural changes in the film and compositional conversions due to the bromination reaction has been performed using SEM and EDS. Based on a preliminary experimental analysis as well as the advantages of a film type reactant, one can conclude that the calcium oxide film may be a feasible alternative to a pellet-type reactant.

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