A non-resonant Kβ valence-to-core X-ray emission approach for fluorine and oxygen differentiation in Zr compounds.

Abstract

Valence-to-core (VtC) X-ray emission spectroscopy (XES) is a powerful probe for the local electronic structure in transition-metal materials, but its potential for 4d metals such as zirconium remains largely unexplored. Here, we demonstrate that non-resonant Zr Kβ VtC XES provides quantitative descriptors that are sensitive to ligand chemistry, by probing fluorine- and oxygen-based coordination environments in well-defined and catalytically relevant Zr compounds. High-resolution X-ray emission spectra containing Zr-Kβ₂ and -Kβ₄ are recorded for a series of reference systems (ZrO₂, ZrF₄, ZrF₄·H₂O, ZrCl₄, Zr(acac)₄, Zr metal) and for Zr fluoride materials, and are analysed using quantitative line-shape parameters. Projected densities of states (PDOS) obtained from FDMNES calculations reveal that fluorine coordination enhances the Kβ″ contribution and induces characteristic changes in Kβ₂ intensity and asymmetry compared to oxygen and chlorine ligands. These ligand-specific spectral signatures enable a systematic discrimination between F- and O-containing coordination spheres, even when conventional X-ray absorption or diffraction techniques provide limited contrast. This combined experimental-computational framework demonstrates that Zr Kβ VtC XES can resolve subtle ligand-dependent coordination changes in Zr-based materials, offering a general route to identify active structures in C-F bond activation and oxygen-evolution catalysis.