A BaFeO 3−δ (δ ≈ 0.22) perovskite was prepared by a sol−gel method and essayed as a catalyst in the CO oxidation reaction. BaFeO 3−δ (0.22 ≤ δ ≤ 0.42) depicts a 6H perovskite hexagonal structural type with Fe in both III and IV oxidation states and oxygen stoichiometry accommodated by a random distribution of anionic vacancies. The perovskite with the highest oxygen content, BaFeO 2.78 , proved to be more active than its lanthanide-based counterparts, LnFeO 3 (Ln = La, Sm, Nd). Removal of the lattice oxygen detected in both temperature-programmed oxidation (TPO) and reduction (TPR) experiments at around 500 K and which leads to the complete reduction of Fe 4+ to Fe 3+ , i.e. to BeFeO 2.5 , significantly decreases the catalytic activity, especially in the lowtemperature range. The analysis of thermogravimetric experiments performed under oxygen and of TPR studies run under CO clearly support the involvement of lattice oxygen in the CO oxidation on these Ba-Fe perovskites, even at the lowest temperatures. Atomically resolved images and chemical maps obtained using different aberration-corrected scanning transmission electron microscopy techniques, as well as some in situ type experiments, have provided a clear picture of the accommodation of oxygen nonstoichiometry in these materials. This atomicscale view has revealed details of both the cation and anion sublattices of the different perovskites that have allowed us to identify the structural origin of the oxygen species most likely responsible for the low-temperature CO oxidation activity.

Chemical and structural features in Fe and Ti manganese doped hollandites are reported by diffraction and advanced imaging techniques.

An impressive library of functional oxide nanomaterials is now available, encompassing multicompartment nanoparticles and heterostructures in general that enable further tuning of the properties. Nonetheless, the vast majority of these nano-objects is built on relatively common oxides, easily synthesized at the nanoscale by chemical methods known since decades. This range of nanoscaled oxides is narrow compared to the library of bulk oxides. Extending the portfolio of oxide compositions at the nanoscale is mandatory to strengthen research efforts on the role of the nanoscale on the properties, and on the emergence of new properties. This chapter provides an overview of the synthesis techniques developed since few years to address complex oxide nanomaterials, encompassing multicationic oxides, oxides of metals with uncommon oxidation states, and new oxide crystal structures accessible only at the nanoscale.For each case, we illustrate the relevance of targeting such complex oxides by discussing their specific properties. doctoral researcher. His main interest is the synthesis design of multifunctional nanomaterials for their application in electrocatalysis.

The high reactivity of silicon nanoparticles provides a low temperature pathway to sodium silicide, an important inorganic precursor to silicon-based materials, including clathrates.