Electrochemical Surface Analysis of Nonconducting Solids: Ferricyanide and Phenol as Electrochemical Probes of the Surfaces of Layered Double Hydroxide Anion‐Exchanging Clays

Abstract

Cyclic voltammetry may be added to the limited repertoire of methods that may be used to examine solid/solution interphases for nonconductive solids, and to select nonconductive solids as heterogeneous electrocatalysts. Hexacyanoferrate(III) was used as an electroactive probe to determine the availability of Zn2+ and Al3+ ions at the surface of a layered double hydroxide (LDH, or hydrotalcite‐like clay, anion exchanging clay, or mixed metal hydroxide). The solid LDH, was applied to the surface of a glassy carbon electrode via its suspension in polystyrene/methylene chloride solution. Cyclic voltammetric experiments showed formation of a Prussian blue‐like film on the surface of the LDH, showing that the zinc and aluminum sites were available to form complexes with species in solution. No film formed on the Mg/Al/Cl analog, or on , , or . Electro‐oxidation of phenol was catalyzed by the Mg/ Al/Cl LDH, but not by the Zn/Al/Cl compound. These results were used to assign effective pH values of >11.2 and 8.3, respectively, for the surfaces of these solids. Electrochemical results are compared with those obtained using x‐ray photoelectron spectroscopy (XPS).