Hydrogen Fluoride Solvent System VIII. A Study of the System NiF<sub>2</sub>-HF-H<sub>2</sub>O.

Clifford, A. F.; Tulmello, A. C.

doi:10.1021/je60018a042

Cited by 4 publications

(2 citation statements)

References 7 publications

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“…In view of the known reactivity of Ni toward HF, however, the first of these alternatives appears highly unlikely. 8 Unfortunately, the XPS instrument employed for these measurements lacks lateral resolution and, therefore, is insensitive to surface inhomogeneities. As shown in the following section, however, AFM images obtained for a nickel film exposed to vapor-phase AHF showed a relatively uniform surface corrugation, without any crevices or discontinuities at the nanometer level and, thus, consistent with a rather continuous nickel fluoride film on the metal surface.…”

Section: Xps Analysis Ofmentioning

confidence: 99%

X-Ray Photoelectron Spectroscopy and Morphological Studies of Polycrystalline Nickel Surfaces Exposed to Anhydrous HF

Totir

Chottiner

Gross³

et al. 2000

J. Electrochem. Soc.

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The Simons electrochemical fluorination (ECF) process is an important method for the electrosynthesis of a variety of perfluorinated organic compounds of commercial interest. 1 The electron/ atom-transfer reactions associated with this complex process are believed to occur on sites on, or within a film formed on Ni anodes polarized at very high potentials, ca. 5-6 V vs. a hydrogen-evolving Ni counter electrode, in solutions of the organic precursors in liquid anhydrous HF (AHF). Although the film undoubtedly contains one or more forms of nickel fluoride, its structure and composition, as well as the detailed ECF reaction mechanism still remain to be elucidated. [1][2][3] The approach implemented at Case Western Reserve University (CWRU) involves a detailed ex situ characterization of Ni anode surfaces following electrofluorination using X-ray photoelectron spectroscopy (XPS) and, as such, it shares some commonalities with the work of Watanabe, 4 who examined with that same technique various aspects of the surface composition of Ni anodes in watercontaining HF solutions. Much of the emphasis in our laboratory has been placed on developing methodologies aimed at minimizing surface contamination before, during, and after electrochemical experiments. As with many other electrochemical processes, impurities present on, or within the electrode, and/or in the electrolyte solution, may play a role in controlling reaction pathways and faradaic efficiencies, i.e., fraction of the current involved in the generation of a specific product. 5 It is precisely one of the primary aims of this research to establish whether such contaminants can alter, among other factors, the nature and distribution of products, by using optimum conditions of cleanliness to perform electrochemical experiments. To this end, a portable ultrahigh vacuum (UHV)-compatible chamber was designed and constructed that allows the transfer of clean and characterized Ni samples between a UHV system that houses the XPS spectrometer and another UHV-compatible chamber where chemical and electrochemical experiments can be carried out.This paper summarizes the results of nonelectrochemical experiments involving exposure of nominally clean polycrystalline Ni foils to both vapor-phase and liquid-phase AHF, using this transfer technique. A comparison between the extent of fluorination of Ni surfaces, based on the relative intensities of XPS features ascribed to nickel(II) fluoride and metallic nickel, indicates that the reactivity of bare Ni toward gas-phase AHF appears to be much higher than toward liquid AHF. Certain aspects of the reactivity of Ni to gasphase AHF were also examined by exposure of thin, smooth Ni films sputtered onto sapphire to gas-phase AHF and subsequent characterization by scanning electron microscopy (SEM) and atomic force microscopy (AFM). ExperimentalThe preparation and characterization of clean Ni surfaces as well as the acquisition of XPS spectra were performed in a multitechnique system equipped with a Perkin-Elmer PHI 5000 Series electron...

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Section: Xps Analysis Ofmentioning

confidence: 99%

X-Ray Photoelectron Spectroscopy and Morphological Studies of Polycrystalline Nickel Surfaces Exposed to Anhydrous HF

Totir

Chottiner

Gross³

et al. 2000

J. Electrochem. Soc.

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show abstract

“…This proposal is supported by the observation that water is required to stabilize the high valent nickel species in nickel oxide (13b). However, the water-dependent phase changes of nickel fluoride (9) and the amorphous or microcrystalline nature of anodic nickel fluoride should also affect conductivity.…”

Section: Fluoride Anode In Wet Hfmentioning

confidence: 99%