On the Scope of XPS as Sensor in Coordination Chemistry of Transition Metal Hexacyanometallates

Abstract

This study reports an evaluation on the scope of X‐ray photoelectron spectroscopy (XPS) to obtain information for the coordination chemistry of transition metal (Tn) hexacyanometallates, TxAz[Mm(CN)6]y where nx +z = y(6 – m), A is an alkaline charge‐compensating cation, and Mm is a transition metal with a maximum of 6 electrons in its nd orbitals. XPS provides an elegant picture on the role of the CN π‐back bonding effect to determine the charge density on the N atom and, from this fact, on its coordination to transition metal ions to form coordination polymers. XPS appears to be able to discriminate between octahedral and tetrahedral coordination for the outer metal (T) to the N end of CN ligands, particularly when the XPS peak and the Auger lines are combined. A similar performance was observed when this spectroscopic technique is used to identify when the CN ligand is found with linear and bifurcated coordination mode to the metal linked at its N end. These last two structural features are relevant in the coordination of metal hexacyanometallates and determine their physical and functional properties. The results obtained from XPS data were correlated with the a priori information from IR spectra and the reported crystal structures for all the samples under study.

Model Studies on the Formation of the Solid Electrolyte Interphase: Reaction of Li with Ultrathin Adsorbed Ionic‐Liquid Films and Co3O4(111) Thin Films

“…Though a rigorous assignment of this new peak is difficult, we tentatively propose that LiCN might be formed. Related compounds such as the lithium tetracyanoquinodimethane charge‐transfer complex (Li−TCQN) shows a BE of 398.6 eV [73] and KCN of 398 eV [74] . After post‐deposition of ≥0.7 MLE of Li, preferentially the N BMP peak stepwise decreases in intensity and is almost completely absent after the last Li dose.…”

“…Related compounds such as the lithium tetracyanoquinodimethane charge-transfer complex (LiÀ TCQN) shows a BE of 398.6 eV [73] and KCN of 398 eV. [74] After post-deposition of � 0.7 MLE of Li, preferentially the N BMP peak stepwise decreases in intensity and is almost completely absent after the last Li dose. Interestingly, at this point, the N TFSI peak does not decrease any further, even if for all other TFSI-related peaks, we monitored a continuous decrease upon increasing the amount of Li (see description of F TFSI and O TFSI above and C TFSI and S TFSI below in the text).…”

Topotactically constructed nickel–iron (oxy)hydroxide with abundant in-situ produced high-valent iron species for efficient water oxidation

“…In addition, the observed Fe II in the XPS spectrum of NiFe 0.2 -Fe PBA (Fig. S4b) can be reasonably explained as that Fe III was partially reduced under X-ray irradiation [31].…”

“…As shown in Fig. S5(a), down, the main O 1s peak at 532.5 eV and the small O 1s peak at 529.9 eV for NiFe 0.2 -Fe PBA should be assigned to the water of crystallization and the very weak oxidation of the surface layer to Ni(Fe)-oxides, respectively [31].…”

“…The peaks observed at the binding energies of the N 1s XPS spectra of NiFe 0.2 -O x H y centered at 398.0 eV and NiFe 0.2 -Fe PBA centered at 398.2 eV can be assigned to cyanogroup (Fig. S5b) [31]. The N 1s peak of NiFe 0.…”