Electro-deposition and stripping of catalytically active iron metal nanoparticles at boron-doped diamond electrodes

Abstract

A new methodology for the electro-deposition and stripping of highly reactive iron nanoparticles at boron-doped diamond electrodes is proposed. In aqueous 1 M NH4F iron metal readily and reversibly electro-deposits onto boron-doped diamond electrodes. The effects of deposition potential, FeF3-6 concentration, deposition time, and mass transport are investigated. Power ultrasound (24 kHz, 8 W cm-2) is employed to achieve enhanced mass transport conditions. Scanning electron microscopy images of iron nanoparticles grown to typically 20-30 nm diameter are obtained. It is shown that a strongly and permanently adhering film of iron at boron-doped diamond can be formed and transferred into other solution environments. The catalytic reactivity of iron nanoparticle deposits at boron-doped diamond is investigated for the reductive dehalogenation of trichloroacetate. The kinetically limited multi-electron reduction of trichloroacetate is dependent on the FeF3-6 deposition conditions and the solution composition. It is demonstrated that a stepwise iron catalysed dechlorination via dichloroacetate and monochloroacetate to acetate is feasible. This methodology in conjunction with power ultrasound offers a novel, clean, and very versatile electro-dehalogenation methodology. The role of fluoride in the surface electrochemistry of iron deserves further attention.