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Probing the Local Environment in Potassium Salts and Potassium-Promoted Catalysts by Potassium Valence-to-Core X-ray Emission Spectroscopy

Year: 2024
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide Potassium plays an important role in biology as well as a promoter in heterogeneous catalysis. There are, however, limited characterization techniques for potassium available in the literature. This study elucidates the potential of element-selective X-ray emission spectroscopy (XES) for characterizing the coordination environment and the electronic properties of potassium. A series of XES measurements were conducted, primarily focusing on the VtC transition (Kβ 2,5 ) of potassium halides (KCl, KBr, and KI) and oxide-bound potassium salts, including potassium nitrate (KNO 3 ) and potassium carbonate (K 2 CO 3 ). Across the series of potassium halides, the VtC transition energy is observed to increase, as accurately reproduced by TDDFT calculations. Molecular orbital analysis suggests that the Kβ 2,5 transition is primarily derived from halide n p contributions, with the primary factor influencing the energy shift being the metal–ligand distances. For oxide ligands, an additional Kβ″ transition appears alongside the Kβ 2,5, which is attributed to a low-energy ligand n s, as elucidated by theoretical calculations. Finally, the XES spectra of two potassium-promoted catalysts for ammonia decomposition/synthesis were measured. These spectra show that potassium within the catalyst is distinct from other K salts in the VtC region, which could be promising for understanding the role of potassium as an electronic promoter.
DOI: 10.1021/acs.inorgchem.4c02069
Language: English
Subfield: Radiation
Open Access status: hybrid
Estimated APC paid: $4,500
OpenAlex ID: W4401715696
FWCI: 1.156
Cites: 61
Cited by: 4
Related to: 10