Al-Taweel, S. / Nadeem, M.A. / Idriss, H. (2022)

Energy Technol., 2022,10, 2100491

Thermal water splitting over 1550C-reduced CeO2and Ce0.95Fe0.05O2δisstudied. Hydrogen production over Ce0.95Fe0.05O2δwas found to be equal to2.53104molðH2Þg1oxidewhich is higher than that observed on CeO2. Thereaction kinetics for Ce0.95Fe0.05O2δis also found to be faster. The oxidesare studied by X-ray diffraction, temperature programmed reduction, andscanning transmission electron microscopy (STEM). XRD results show that Fe issubstituted for Ce4þin the as prepared oxides. Fe3þcations substitution alsodecreases the CeO2crystallites size. Heating to 1100C increases their size,although the Fe-containing oxide still shows smaller crystallites when comparedwith CeO2alone. The activation energy for surface reduction of CeO2, extractedfrom TPR, is found to be slightly higher (1.58 eV) than that of bulk reduction(1.43 eV). While high resolution TEM and electron energy loss spectroscopybefore reaction show that Fe cations are homogenously distributed, thoseafter reaction show in addition to the growth of the crystallites size, Fe segre-gation to the edges of the crystals, although no detachment of Fe oxide particlesis seen. The mechanism of water dissociative adsorption and hydrogenre-combinative desorption is discussed in which the role of Ce–O–Fe sites isconsidered.

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