Using soft-x-ray diffraction at the site-specific resonances in the Fe L2,3 edge, we find clear evidence for orbital and charge ordering in magnetite below the Verwey transition. The spectra show directly that the (001/2) diffraction peak (in cubic notation) is caused by t2g orbital ordering at octahedral Fe2+ sites and the (001) by a spatial modulation of the t2g occupation.
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http://dx.doi.org/10.1103/PhysRevLett.100.026406 | DOI Listing |
Angew Chem Int Ed Engl
November 2024
Beijing Key Laboratory of Environmental Science and Engineering, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081, PR China.
MOFs-like polyoxometalate (POMs) electrodes, harvesting combined advantages of interlocking porosity and multi-electron transfer reaction, have already emerged as promising candidates for lithium-ion batteries (LIBs), yet the origins of the underlying redox mechanism in such materials remain a matter of uncertainty. Of critical challenges are the anomalously high storage capacities beyond their theoretical values and the fast ion diffusivity that cannot be satisfactorily comprehended in the theory of crystal lattice. Herein, for the first time we decode t electron occupation-regulated dual-redox Li-storage mechanism as the true origin of extra capacity in POMs electrodes.
View Article and Find Full Text PDFChemSusChem
November 2024
Key Laboratory of Energy Thermal Conversion and Control of, Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China.
The orbital modulation and surface lattice reconstruction represent an effective strategy to regulate the interaction between catalyst interface sites and intermediates, thereby enhancing catalytic activity and selectivity. In this study, the crystal surface of Au-K/CeO catalyst can undergo reversible transformation by tuning the coordination environment of Ce, which enables the activation of the C-H bond and the oxidative cleavage of the C and C-C bonds, leading to the cleavage of 2-phenoxy-1-phenylethanol. The t orbitals of Au 5d hybridize with the 2p orbitals of lattice oxygen in CeO via π-coordination, modulating the coordination environment of Ce 4 f and reconstructing the lattice oxygen in the CeO framework, as well as increasing the oxygen vacancies.
View Article and Find Full Text PDFAdv Mater
December 2024
Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China.
ChemSusChem
November 2024
School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou City, Jiangsu Province, 225002, China.
Integrating oxygen redox reactions with transition metal redox reactions offers a promising strategy to double or triple the energy density for large-capacity battery cathodes. In this study, we have introduced intrinsic oxygen vacancies (V) into a P3 layered cathode to modulate the electronic structure of O atoms and enhance oxygen redox activity. Rietveld-refined X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and X-ray photoelectron spectroscopy confirm the successful creation of V in NaMnMgO (OV-NMM).
View Article and Find Full Text PDFAdv Mater
January 2025
Beijing National Center for Electron Microscopy and Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China.
Li-ion batteries employing stoichiometric layered Li metal oxides as cathodes are now reaching the energy density limits due to single cationic redox chemistry. Lattice oxygen redox (LOR) has been discovered in these materials, as a high-energy-density paradigm observed in Li-rich materials. Nevertheless, the origin of this process is not understood, preventing the rational design of better cathode materials.
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