The crystal structure of LnFeAsO 1Ày (Ln = La, Nd) has been studied by the powder neutron diffraction technique. The superconducting phase diagram of NdFeAsO 1Ày is established as a function of oxygen content which is determined by Rietveld refinement. The small As-Fe bond length suggests that As and Fe atoms are connected covalently. FeAs 4 -tetrahedrons transform toward a regular shape with increasing oxygen deficiency. Superconducting transition temperatures seem to attain maximum values for regular FeAs 4 -tetrahedrons.

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The design of active and durable catalysts for the H 2 O/O 2 interconversion is one of the major challenges of electrocatalysis for renewable energy. The oxygen evolution reaction (OER) is catalyzed by SrRuO 3 with low potentials (ca. 1.35 V RHE ), but the catalyst’s durability is insufficient. Here we show that Na doping enhances both activity and durability in acid media. DFT reveals that whereas SrRuO 3 binds reaction intermediates too strongly, Na doping of ~0.125 leads to nearly optimal OER activity. Na doping increases the oxidation state of Ru, thereby displacing positively O p-band and Ru d-band centers, weakening Ru-adsorbate bonds. The enhanced durability of Na-doped perovskites is concomitant with the stabilization of Ru centers with slightly higher oxidation states, higher dissolution potentials, lower surface energy and less distorted RuO 6 octahedra. These results illustrate how high OER activity and durability can be simultaneously engineered by chemical doping of perovskites.

Li sites and occupancies are determined by neutron diffraction of cubic Al-free Li7La3Zr2O12. Maximum 7.5 Li per formula unit in the garnet formwork can be determined from the model, with half of the tetrahedral sites vacant and long-range ordered.