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A Ce 2 Zr 2 O 8 mixed oxide was prepared, and the influence of redox treatments on its reduction behavior was systematically analyzed. The temperature of reduction was found to change on application of redox cycles under severe conditions, with the final appearance of temperature-programmed reduction profiles dictated by the exact conditions employed in the redox cycle (temperature of treatment and concentration of H 2 ). In addition, the conditions necessary in the reducing and oxidizing parts of the redox cycle showed interdependence. The reduction was found to vary from a single high-temperature peak to a single lowtemperature peak, via double-peak profiles with various relative intensities. Structural analysis of the sample after application of analogous treatments indicated that the reduction behavior follows a pathway, with t′ and κ phases at the two extremes (high-and low-temperature single-peak profiles). The latter phase contains pyrochlore-type cation ordering. However, bulk ordering is not necessary to promote low-temperature reduction. The evidence suggests that the two-peak profiles are observed when cation ordering is very limited, and a single low-temperature peak is observed when domains of the κ phase coexist with larger amounts of the t′ phase. Thus, even the presence of partial ordering at the surface is sufficient to produce an effect.

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Hybrid organic-inorganic perovskites, MAPbX (X = halogen), containing methylammonium (MA: CH-NH) in the large voids conformed by the PbX octahedral network, are the active absorption materials in the new generation of solar cells. CHNHPbBr is a promising member with a large band gap that gives rise to a high open circuit voltage. A deep knowledge of the crystal structure and, in particular, the MA conformation inside the perovskite cage across the phase transitions undergone below room temperature, seems essential to establish structure-property correlations that may drive to further improvements. The presence of protons requires the use of neutrons, combined with synchrotron XRD data that help to depict subtle symmetry changes undergone upon cooling. We present a consistent picture of the structural features of this fascinating material, in complement with photocurrent measurements from a photodetector device, demonstrating the potential of MAPbBr in optoelectronics.

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The effect of vanadium oxide loading on CeO 2 support for ethane oxidative dehydrogenation (ODH) is studied. Surface vanadia species are highly dispersed on CeO 2 . The interaction with surface vanadia species significantly changes the structural and reactive properties of ceria support. VO x /CeO 2 suffers an important change during ethane ODH due to a solid-state reaction between CeO 2 and surface vanadia species resulting in the formation of CeVO 4 . Such a solid-state reaction is promoted by high temperature, high vanadium loading, and reducing environments. Raman in situ temperature-programmed studies under reduction and oxidation conditions reveal that the catalytic cycle involves oxidation-reduction of the Ce 4+ T Ce 3+ species, while the V 5+ species remain stable.