Electrocatalysis at Co–poly(difluoropyrrole) electrodeposited on Vulcan carbon supports: demonstration of halogenated polypyrrole as an electrocatalytic material

Abstract

Halogenated polypyrroles are rendered significantly more stable against oxidative degradation than native polypyrrole and the electron-withdrawing substituents also permit tuning of the electronic state of coordinated catalytic metal ions. Poly(difluoropyrrole), or poly(dfp), was deposited on high-surface-area Vulcan carbon (VC) via bulk electrolytic oxidation of the monomer 3,4-difluoropyrrole at VC slurried in (n-C₄H₉)₄NClO₄/acetonitrile; the carbon-supported polymer was subsequently metallated with cobalt(II) ions. As determined by thermal, micrographic, elemental, and chemical state analyses, the Co-poly(dfp)/VC composite is ∼7 wt% poly(dfp) with the polymer inhomogeneously deposited over the Vulcan carbon, and the incorporated Co(II) ions coordinated by nitrogen atoms in the pyrrole moieties. Films of Co-poly(dfp)/VC cast on glassy carbon disk electrodes are electrocatalytically active for the two-electron reduction of oxygen in 0.1 M aqueous perchloric acid as assessed by hydrodynamic voltammetry, thereby demonstrating the viability of halogenated polypyrroles as electrocatalytic materials.