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Highlights • Local measurements of magnetic circular dichroism, atomic arrangement, cation order, chemical state and elemental distribution from the very same region provide an improved understanding of structure-property relationships at the nm scale in double perovskites with different structural complexities. • Antiferromagnetic Fe3+-O2−-Fe3+superexchange interactions arising from an excess of Fe suppress the magnetic circular dichroism signal from Fe cations in ordered Sr 2 [Fe][Fe 1/5 Re 4/5 ]O 6 , when compared with ordered Sr 2 [Fe][Re]O 6. • Dominant Fe3+-O2−-Fe3+antiferromagnetic coupling in disordered Sr[Fe 4/5 Re 1/5 ]O 3 leads to a decrease in magnetic circular dichroism signal down to the noise level. Abstract Superexchange-based magnetic coupling of the two B -site cations in rock-salt-ordered double perovskite oxides is extremely sensitive to the cation ratio and degree of order. However, as a result of the limited spatial resolution of most magnetic characterization techniques, it is challenging to establish a direct relationship between magnetic properties and structure in these materials, including the effects of elemental segregation and cation disorder. Here, we use electron energy-loss magnetic chiral dichroism together with aberration-corrected electron microscopy and spectroscopy to record magnetic circular dichroism (MCD) spectra at the nm scale, in combination with structural and chemical information at the atomic scale from the very same region. We study nanoscale phases in ordered Sr 2 [Fe][Re]O 6 , ordered Sr 2 [Fe][Fe 1/5 Re 4/5 ]O 6 and disordered Sr[Fe 4/5 Re 1/5 ]O 3 individually, in order to understand the role of cation ratio and order on local magnetic coupling. When compared with ordered Sr 2 [Fe][Re]O 6 , we find that antiferromagnetic Fe3+-O2−-Fe3+superexchange interactions arising from an excess of Fe suppress the MCD signal from Fe cations in ordered Sr 2 [Fe][Fe 1/5 Re 4/5 ]O 6 , while dominant Fe3+-O2−-Fe3+antiferromagnetic coupling in disordered Sr[Fe 4/5 Re 1/5 ]O 3 leads to a decrease in MCD signal down to the noise level. Our work demonstrates a protocol that can be used to correlate crystallographic, electronic and magnetic information in materials such as Sr 2 Fe 1+ x Re 1- x O 6 , in order to provide insight into structure-property relationships in double perovskite oxides at the atomic scale. [ABSTRACT FROM AUTHOR]

Catalytic NH 3 synthesis and decomposition offer a new promising way to store and transport renewable energy in the form of NH 3 from remote or offshore sites to industrial plants. To use NH 3 as a hydrogen carrier, it is important to understand the catalytic functionality of NH 3 decomposition reactions at an atomic level. Here, we report for the first time that Ru species confined in a 13X zeolite cavity display the highest specific catalytic activity of over 4000 h -1 for the NH 3 decomposition with a lower activation barrier, compared to most reported catalytic materials in the literature. Mechanistic and modeling studies clearly indicate that the N-H bond of NH 3 is ruptured heterolytically by the frustrated Lewis pair of Ru δ+ -O δ- in the zeolite identified by synchrotron X-rays and neutron powder diffraction with Rietveld refinement as well as other characterization techniques including solid-state nuclear magnetic resonance spectroscopy, in situ diffuse reflectance infrared transform spectroscopy, and temperature-programmed analysis. This contrasts with the homolytic cleavage of N-H displayed by metal nanoparticles. Our work reveals the unprecedented unique behavior of cooperative frustrated Lewis pairs created by the metal species on the internal zeolite surface, resulting in a dynamic hydrogen shuttling from NH 3 to regenerate framework Brønsted acid sites that eventually are converted to molecular hydrogen.

The catalytic synthesis of NH 3 from the thermodynamically challenging N 2 reduction reaction under mild conditions is currently a significant problem for scientists. Accordingly, herein, we report the development of a nitrogenase-inspired inorganic-based chalcogenide system for the efficient electrochemical conversion of N 2 to NH 3 , which is comprised of the basic structure of [Fe-S 2 -Mo]. This material showed high activity of 8.7 mg NH 3 mg Fe -1 h -1 (24 μg NH 3 cm -2 h -1 ) with an excellent faradaic efficiency of 27% for the conversion of N 2 to NH 3 in aqueous medium. It was demonstrated that the Fe 1 single atom on [Fe-S 2 -Mo] under the optimal negative potential favors the reduction of N 2 to NH 3 over the competitive proton reduction to H 2 . Operando X-ray absorption and simulations combined with theoretical DFT calculations provided the first and important insights on the particular electron-mediating and catalytic roles of the [Fe-S 2 -Mo] motifs and Fe 1 , respectively, on this two-dimensional (2D) molecular layer slab., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

Catalytic conversion of methanol to aromatics and hydrocarbons is regarded as a key alternative technology to oil processing. Although the inclusion of foreign metal species in H-ZSM-5 containing Brønsted acid site (BAS) is commonly found to enhance product yields, the nature of catalytically active sites and the rationalization for catalytic performance still remain obscure. Herein, by acquiring comparable structural parameters by both X-ray and neutron powder diffractions over a number of metal-modified ZSM-5 zeolites, it is demonstrated for the first time that active pairs of metal site-BAS within molecular distance is created when single and isolated transition metal cation is ion-exchanged with the zeolites. According to our DFT model, this could lead to the initial heterolytic cleavage of small molecules such as water and methanol by the pair with subsequent reactions to form products at high selectivity as that observed experimentally. It may account for their active and selective catalytic routes of small molecule activations., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)