Structural and Electronic Effects of X-ray Irradiation on Prototypical [M(COD)Cl]2 Catalysts

Abstract

X-ray characterisation techniques are invaluable for probing material characteristics and properties, and have been instrumental in discoveries across materials research. However, there is a current lack of understanding of how X-ray induced effects manifest in small molecular crystals. This is of particular concern as new X-ray sources with ever increasing brilliance are developed. In this paper, systematic studies of X-ray-matter interactions are reported on two industrially important catalysts, [Ir(COD)Cl]2 and [Rh(COD)Cl]2, exposed to radiation in X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) experiments. From these complimentary techniques, changes to structure, chemical environments, and electronic structure are observed as a function of X-ray exposure, allowing comparisons of stability to be made between the two catalysts. Radiation dose is estimated using recent developments to the RADDOSE-3D software for small molecules and applied to powder XRD and XPS experiments. Further insights into the electronic structure of the catalysts and changes occurring as a result of the irradiation are drawn from density functional theory (DFT). The techniques combined here offer much needed insight into the X-ray induced effects in transition metal catalysts and consequently, their intrinsic stabilities. There is enormous potential to extend the application of these methods to other small molecular systems of scientific or industrial relevance.

Metal–Support Interaction Can Deactivate IrOx/Sb:SnO2 OER Catalysts in Polyol Process

“…Binding energies (BEs) of Ir 4f for the precursor used are reported to be 61.3 eV (4f 7/2 ) and 64.3 eV (4f 5/2 ), which correspond to the Ir 1+ 4f doublet. 31,32 Samples prepared at 100 °C show the Ir 1+ oxidation states (Figure 3C), indicating that the precursor remains unreduced under this synthesis condition. The core level associated with Ir in the zero-oxidation state is 60.9 eV (4f 7/2 ) and 63.9 eV (4f 5/2 ).…”

Oxygen Evolution Electrocatalysis in Acids: Atomic Tuning of the Stability Number for Submonolayer IrOx on Conductive Oxides from Molecular Precursors

“…The binding energies of the 4f 7/2 peaks matched literature values for [(COD)IrCl] 2 . 48 The peak at 61.2 eV was attributed to Ir 1+ while the peak at a higher binding energy was assigned to the hydroxylated Ir surface species. 48 In our case, the high-binding- energy peak likely arises from the topmost layer of the powder degrading in air as the sample is loaded into the XPS chamber.…”

“…48 The peak at 61.2 eV was attributed to Ir 1+ while the peak at a higher binding energy was assigned to the hydroxylated Ir surface species. 48 In our case, the high-bindingenergy peak likely arises from the topmost layer of the powder degrading in air as the sample is loaded into the XPS chamber. The Ir 4f peak of [(COD)IrCl] 2 attached to ATO nanopowder was fit with one set of Ir 4f peaks (4f 7/2 centered at 62.0 eV) (Figure 2a).…”