Solar thermochemical process for hydrogen production via two-step water splitting cycle based on Ce1−xPrxO2−δ redox reaction

Ce1−xPrxO2−δ (x = 0, 0.05, 0.1, 0.2 and 0.3), as reactive ceramics synthesized by combustion method for H2 production via two-step water splitting reaction with concentrated solar energy, was investigated in present work. XRD analysis of the samples shows that Pr6O11 underwent a phase transition into Pr2O3and Pr2O3 cannot be oxidized by steam to yield H2 in two-step water splitting reaction. The solid solutions of the samples containing Ce were formed with a single cubic CeO2 fluorite structure after synthesis and even after two-step water splitting reaction. Although Pr cannot be oxidized by steam to generate H2 in two-step water splitting reaction, the promotion effect is present with the introduction of 5 mol% and 10 mol% Pr into CeO2 on the amounts of O2 and H2, but the volume of H2 evolved is enhanced or not, strongly dependent on the H2-generation temperature. The optimum H2-generation temperature is 1023 K.

Research highlights
► Ce1−xPrxO2−δ was used for hydrogen production via two-step water splitting reaction.
► The increase in volumes of O2 and H2 evolved depends on Pr content and H2-generation temperature.
► The optimal Pr content for hydrogen production is 10 mol% Pr in CeO2.
► The optimal H2-generation temperature in H2-generation reaction is 750 °C.