Cerium ion redox system in CeO2–xFe2O3 solid solution at high temperatures (1,273–1,673 K) in the two-step water-splitting reaction for solar H2 generation

• Published in: Journal of materials science Vol. 43; no. 9; pp. 3153 - 3161
• Main Authors: Kaneko, H, Ishihara, H, Taku, S, Naganuma, Y, Hasegawa, N, Tamaura, Y
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.05.2008; Springer Nature B.V
• Subjects: atomic absorption spectrometry; ceramics; cerium; Cerium oxides; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; combustion; Crystallography and Scattering Methods; gases; hydrogen; Hydrogen production; image analysis; Infrared imaging; irradiation; Materials Science; Mossbauer spectroscopy; Oxidation; oxygen; Polymer Sciences; Solid Mechanics; Solid solutions; solutions; temperature; Water splitting; X-radiation; Fluorite Structure; CeO2; Quartz Tubular Reactor; Hyperfine Magnetic Field; Isomer Shift
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-008-2499-z

CeO₂–xFe₂O₃ (x = 0.026–0.214) solid solutions with different Ce:Fe mole ratios (Ce:Fe = 9.5:0.5–7.0:3.0) were prepared as reactive ceramics with the combustion method for solar hydrogen production. The prepared CeO₂–xFe₂O₃ solid solutions were characterized by X-ray diffractometry, ICP atomic emission spectrometry, and Mössbauer spectroscopy. Two-step water-splitting reaction with the CeO₂–xFe₂O₃ solid solution proceeded at 1,673 K for the O₂-releasing reaction and at 1,273 K for the H₂-generation reaction by irradiation of an infrared imaging lamp as a solar simulator. The amounts of H₂ gas evolved in the H₂-generation reaction with CeO₂–xFe₂O₃ solid solutions were 0.97–1.8 cm³/g, the evolved H₂/O₂ ratio was approximately equal to 2 of the stoichiometric value. The amounts of H₂ and O₂ gases were independent of the Ce:Fe mole ratio in the CeO₂–xFe₂O₃ solid solution. It was suggested that the O₂-releasing and H₂-generation reactions with the CeO₂–xFe₂O₃ solid solution were repeated with the reduction and oxidation of Ce⁴⁺–Ce³⁺ enhanced by the presence of Fe³⁺–Fe²⁺.