Sonoelectrochemical deposition of catalytically active iron metal at boron-doped diamond electrodes: aplication to electroreduction of chloroacetates

Comunicación presentada en el 19th International Congress on Acoustics, Madrid, 2-7 September 200

M A Muthukumaran, Potentiostatic studies on indirect electrochemical reduction of vat dyes. Dyes and Pigments

Abstract Dispersed vat dyestuffs can be electrochemically reduced by indirect electrolysis using ironetriethanolamine complex as a reducing agent. The application and mechanism of indirect electrolysis as a reduction technique are described in detail in this paper. Electrochemically reduced vat dye is tested on a laboratory scale in dyeing experiments, and the results of different reduction conditions are discussed. The influence of the concentration of the complex-system on the build-up of colour depth, shade and fastness is discussed and compared with samples of the standard dyeing procedure using sodium dithionite as the reducing agent. The new process offers environmental benefits as well as prospects for improved process stability, because the state of reduction in the dye-bath can be readily monitored by measuring the reduction potential

Bismuth Oxychloride Dispersed on Nitrogen-Doped Carbon as Catalyst for the Electrochemical Reduction of CO₂ to Formate

Electrochemical reduction of CO2 has received significant interest for converting CO2 to value added products and closing the carbon cycle. Recent advances through catalyst development have aided in satisfying the requirements of achieving a high product selectivity, activity and long-term stability. Among various industrially valuable products, formic acid has found numerous applications such asin fuel cells and textile industry. In this work, we report the synthesis of bismuth oxychloride dispersed on nitrogen-doped carbon through a facile ion adsorption process using bismuth acetate, hydrochloric acid and urea as precursors, and discuss its performance as an electrocatalyst for the electrochemical reduction of CO2 to formate. The results show that bismuth oxychloride dispersed on nitrogen-doped carbon has good catalytic activity for CO2 reduction to formate in 0.5 M KHCO3, achieving a maximum faradaic efficiency of 84.3 % at −0.87 V versus RHE. The catalyst is found to be stable for 5 h of continuous operation and achieves a turnover frequency of 146.36 h−1.Accepted Author ManuscriptChemE/Materials for Energy Conversion & Storag

Electrocatalytic activity of BasoliteTM F300 metal-organic-framework structures

For the case of the commercially available metal-organic framework (MOF) structure BasoliteTM F300 or Fe(BTC) with BTC = benzene-1,3,5-tricarboxylate, it is shown that the Fe(III/II) electrochemistry is dominated by reductive dissolution rather than ion insertion (which in marked contrast is dominating the behaviour of Fe(III/II) open framework processes in Prussian blues). Solid Fe(BTC) immobilised onto graphite or platinum working electrodes is investigated and it is shown that well-defined and reversible Fe(III/II) reduction responses occur only on platinum and in the presence of aqueous acid. The process is shown to follow a CE-type mechanism involving liberation of Fe(III) in acidic media, in particular for high concentrations of acid. Effective electrocatalysis for the oxidation of hydroxide to O2 (anodic water splitting) is observed in alkaline aqueous media after initial cycling of the potential into the reduction potential zone. A mechanism based on a MOF-surface confined hydrous iron oxide film is proposed. Keywords: MOF, Voltammetry, Prussian blue, Reductive dissolution, Host guest electrochemistry, Water splitting, Senso

Catalytic iron metal nanoparticles at boron-doped diamond electrodes: sonoelectrochemical deposition and stripping

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.This work was supported by the EU COST Programme (Action D32, working groups "Microwave and Ultrasound Activation in Chemical Analysis" and "Electrochemistry with Ultrasound"). V.S. and J.G.-G. thank the Generalidad Valenciana for the financial support by the Project GV05/104