EXAFS and XANES studies of Zn2+ and Rb+ neutralized perfluorinated ionomers

Abstract

Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near 2+ + edge structure (XANES) experiments have been carried out to probe the Zn and Rb environment in perfluorinated ionomers. The cation environment has been determined for these ionomers in their dry, hydrated and n-amyl alcohol swollen state. It was found that a well ordered, crystalline-like nearest-neighbor oxygen shell predominates in the zinc neutralized perfluorinated ionomers. Unlike the zinc ionomers, the Rb § neutralized ionomers show no discernible peaks in the radial structure function indicating that the rubidium environment is highly disordered. Coordination of the hydroxyl groups of namyl alcohol to cations was suggested by EXAFS analysis. XANES analysis was usefulin corroborating the EXAFS information and in providing information about the ionic character of the nearest-neighbor bonding.

Operando Evolution of the Structure and Oxidation State of Size-Controlled Zn Nanoparticles during CO2 Electroreduction

“…9663 eV. These observations allow us to conclude that Zn atoms in the as-prepared NPs likely have octahedral coordination, rather than tetrahedral typical for ZnO and Zn­(Ac) 2 . , Moreover, a similar spectral shape was reported for small ZnO clusters of octahedral structure with size below 3 nm and solvated Zn ions. , Zn undergoes significant reduction during CO 2 RR as indicated by the lower white line intensity in the XANES spectra (Figure a). However, those zinc oxide species do not become completely reduced under CO 2 RR, as evidenced by a slightly higher white line in XANES spectra compared to the Zn foil.…”

Extraction of zinc(II) from ammoniacal solution into hydrophobic ionic liquids

“…The results of fitting EXAFS spectra of the first coordination shell are presented in Table . The XANES spectra show that the relative intensity of the main peak for [BMIM]NTf 2 system is higher than that for [OMIM]PF 6 and [OMIM]NTf 2 systems, which could be attributed to the higher coordination number of the extracted zinc complexes in [BMIM]NTf 2 , . Since water has higher solubility in [BMIM]NTf 2 than [OMIM]PF 6 and [OMIM]NTf 2 , water molecules could coordinate more easily with zinc complexes in [BMIM]NTf 2 .…”

“…Similar to the effect of changes in aqueous pH, this decrease can be also attributed to the formation of zinc ammine complexes. However, when the total ammonia concentration decreases from 3.0 to 1.0 mol L −1 , the extraction of zinc increases from 35 zinc extraction from ammoniacal solutions when the appropriate ammonia concentration was chosen.…”

“…The XANES spectra show that the relative intensity of the main peak for [BMIM]NTf 2 system is higher than that for [OMIM]PF 6 and [OMIM]NTf 2 systems, which could be attributed to the higher coordination number of the extracted zinc complexes in [BMIM]NTf 2 . 34,35 Since water has higher solubility in [BMIM]NTf 2 than [OMIM]PF 6 and [OMIM]NTf 2 , water molecules could coordinate more easily with zinc complexes in [BMIM]NTf 2 . Therefore, the zinc ion in ammoniacal solution could be extracted as hydrated ZnA 2 into ionic liquids.…”

Studies on Indigenous Ion Exchange Resins II: Alkaline Earth Metal Ion-hydrogen Ion Exchange Equilibria

“…At low concentration of the divalent ion in the exchanger, isolated dimers of the ions are formed and at higher cation concentration, ion aggregates are formed (Fig. 2) [7,8].…”