Getting under the surface of aging: The bulk structure of copper nanoparticles can be tailored during the preparation by exploiting known structure–activity relationships. Ageing of freshly precipitated precursors leads to characteristic phase transitions and enables control of microstrain and particle size (see picture) properties which influence catalytic activity.

The synthesis, chemical, structural, and magnetic properties of alkali-metal compounds with filledskutterudite structure, NaFe 4 Sb 12 and KFe 4 Sb 12 , are described. X-ray and neutron diffraction and elemental analysis established the crystal structure without defects and disorder on the cation site. The temperature and pressure dependence of the cubic unit cell of NaFe 4 Sb 12 and the displacement parameter of Na are investigated. The electronic structure is calculated by density functional methods (LMTO, FPLO). Quantum chemical calculations (electron localization function) reveal the covalent character of both Fe-Sb and Sb-Sb interactions. Electronic structure calculations within the local density approximation exhibit a band ferromagnetic ground state and predict a half-metallic behavior. In contrast to isostructural alkaline-earth compounds (CaFe 4 Sb 12 and BaFe 4 Sb 12 ), the alkali-metal skutterudites are itinerant electron ferromagnets with small magnetic moments (Ϸ0.25 B / Fe atom) and T C Ϸ 85 K. Yet the paramagnetic moments of all four compounds are between 1.5 B and 1.7 B per Fe atom, indicating similar Stoner factors. Temperature-dependent 57 Fe and 121 Sb Mössbauer spectroscopies confirm the ferromagnetic state in the sodium compound with very small hyperfine fields at the iron and antimony sites.

Structure-activity relationships of a nanostructured Cu/ZrO 2 catalyst for the steam reforming of methanol (MSR) were investigated under reaction conditions by in situ X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) combined with on-line mass spectrometry (MS). Temperature programmed activation by reduction in hydrogen or by reduction in a mixture of methanol and water (feed) was studied by time-resolved Cu K edge XANES and TG/DSC/MS measurements. Small and disordered CuO particles were identified as the main copper phase present in the precursors. After extended time on stream and treatment at 673 K in hydrogen, no significant sintering of the copper particles or deactivation of the reduced Cu/ZrO 2 catalysts was detected indicating a superior stability of the material. The initially low steam reforming activity of the Cu/ZrO 2 catalyst after reduction in hydrogen could be significantly increased by a temporary addition of oxygen to the feed. This increased activity after oxidative treatment is correlated to an increasing amount of oxygen in the copper particles.63 Cu NMR studies detected only a minor degree of microstrain in the active copper phase of the Cu/ZrO2 catalyst. The decreased reducibility of CuO/ZrO 2 , the low degree of microstrain, and the correlation between the amount of oxygen remaining in the copper particles and the catalytic activity indicate a different metal support interaction compared to Cu/ZnO catalysts.