Organic–Inorganic Hybrid Films of the Sulfate Dawson Polyoxometalate, [S2W18O62]4–, and Polypyrrole for Iodate Electrocatalysis

The Dawson-type sulfate polyoxometalate (POM) [S2W18O62]4– has successfully been entrapped in polypyrrole (PPy) films on glassy carbon electrode (GCE) surfaces through pyrrole electropolymerization. Films of varying POM loadings (i.e., thickness) were grown by chronocoulometry. Film-coated electrodes were then characterized using voltammetry, revealing POM surface coverages ranging from 1.9 to 11.7 × 10–9 mol·cm–2, and were stable over 100 redox cycles. Typical film morphology and composition were revealed to be porous using atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy, and the effects of this porosity on POM redox activity were probed using AC impedance. The hybrid organic–inorganic films exhibited a good electrocatalytic response toward the reduction of iodate with a sensitivity of 0.769 μA·cm–2·μM–1.