Clay modified electrodes. 3. Electrochemical and electron spin resonance study of montmorillonite layers (original) (raw)

1985, Journal of the American Chemical Society

Films (about 30 nm to 3fim thick) of the clay mortmorillonite, with and without added poly(viny1 alcohol) (PVA), were cast on conductive substrates (SnOZ/glass, glassy carbon, platinum) and used as electrodes. Electron spin resonance of the incorporated probe, tempamine, and X-ray diffraction measurements showed that the films with clay alone were oriented, while those containing PVA were random and swollen. The electrochemistry of cationic species incorporated into the films, e.g., Ru(bpy),*+, Os(bpy),*+, Fe(b~y),~+, is described; the effective diffusion coefficients of the Os and Fe species in these films were-cm2 s-'. Neutral (hydroquinone) and several anionic species, while not incorporated into the film, can diffuse through it to the substrate. Chronoamperometric and rotating disk electrode measurements were employed to study this diffusion. Catalytic hydrogen production at a clay/Pt/PVA film containing propyl viologen sulfonate was found. The modification of electrode surfaces by coverage with a thin layer of a treated clay was recently reported from this laboratory.' Cationic species, e.g., R~(b p y) ,~+ (bpy = 2,2'-bipyridine), Fe-(b p~) ,~+ , MV2+ (methyl viologen), could be incorporated into sodium montmorillonite films; for thicker films (ca. 3 fim) clay premixed with poly(viny1 alcohol) (PVA), with or without colloidal platinum, produced more durable films that more readily incor