Application of transmission Mössbauer effect spectroscopy to the study of electrocatalysis and adsorption phenomena at the nickel hydroxide electrode

Abstract

Miissbauer parameters for ferric hydroxo forms in alkaline matrices, ferric oxyhydroxide and its admixture at the nickel hydroxide electrode surface as well as for ferric hydroxo species adsorbed at nickel hydroxides from strongly alkaline solutions have been compared. The feasibility of transmission Miissbauer spectra acquisition for the adsorbed species in the presence of dissolved forms (e.g. in sir#) is based on the principle that the latter give no Miissbauer effect at room temperature owing to their diffusional mobility, while the former, being fixed at the adsorbent surface, have been shown to exhibit a sufiicient resonant absorption. Tbe effects of adsorption and adsorbent surface state on the coordination of ferric hydroxo complexes as well as its hydrolytic destruction in water have been noted. Some questions connected with anodic oxygen evolution electrocatalysis by iron species involved in the anodic process at the nickel hydroxide electrode are also discussed.

Application of transmission Mössbauer spectroscopy to the surface study of Ni(II)–Fe(III) hydroxide electrocatalysts: Comparison with AES data

“…Some other details of Mossbauer experimental procedure concerning sample preparation, apparatus, spectra acquisition and data treatment have been thoroughly described elsewhere. [20][21][22] To perform AES analyses, samples of binary hydroxide powders were carefully pressed into an indium metal platelet and attached to the spectrometer holder. The starting pressure of residual gases in the analysis chamber was 5 x lo-' Pa.…”

“…The latter technique has once again proved to be a highly effective tool, sensitive to various bulk and surface effects (cf. 20,22,37 and 38). It is also noteworthy that, in view of a distinctly exhibited 'surface' effect of ferric species on the anodic oxygen evolution (AOE) kinetics at the nickel hydroxide ele~trode,~'-'~ an essentially higher Fe(II1) concentration in the surface layers of the binary systems studied may well contribute to the excellent electrocatalytic activity towards AOE found for composite Ni-Fe hydroxide sys~tems.…”

Advances and Challenges in Industrial-Scale Water Oxidation on Layered Double Hydroxides

“…The iron incorporation was shown as the main driving force to improve the activity of LDH-based catalysts. It can be introduced intentionally by codeposition or unintentionally from solutions containing already impurity levels of Fe 3+ . ,− For iron uptake from solution, Fe 3+ is first deposited to edge and defect sites, which act as OER active sites . Upon further Fe 3+ uptake, iron is incorporated into the bulk and homogeneously mixed into the Ni-LDH matrix .…”

An improved method of water electrolysis – effect of complexing agent

“…Efficiency in electrolysis can be improved by reducing the cell voltage through the use of catalysts with increased surface area or by changing the nature of the overpotential of the reaction. In AWE anodic overpotential is a major factor that limits the efficiency and hence is researched frequently [4][5][6]. Ni based electrodes, being less corrosive in alkaline solution, offer low cost solution despite its higher overpotential in alkaline solutions when compared to costly RuO 2 and IrO 2 based catalyst used in acidic media [7].…”