Efficient oxygen reduction in alkaline solution with platinum phthalocyanine on porous carbon

Porous carbon electrodes coated with platinum phthalocyanine are found to be stable at 35°C towards electroreduction of oxygen in concentrated alkali. Moreover, the concentration of Pt is substantially reduced relative to an electrode carrying dispersed Pt

High efficiency cathodes for alkaline air electrodes

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Graphene-modified electrode. Determination of hydrogen peroxide at high concentrations.

A gold electrode partially coated by graphene multilayer is developed and tested with respect to high concentrations of hydrogen peroxide. The effective use of conventional electrode materials for the determination of such an analyte by anodic oxidation or cathodic reduction is prevented by the occurrence of adsorptions fouling the electrode surface. This prevents reliable and repeatable voltammetric curves for being recorded and serious problems arise in quantitative analysis via amperometry. The gold–graphene electrode is shown to be effective in quantitative evaluation, by cathodic reduction, of hydrogen peroxide at concentration levels that are of interest in an industrial. Acid, neutral, and basic pH values have been tested through correct adjustment of a Britton Robinson buffer. The experiment s have been performed both by cyclic voltammetry and with amperometry at constant potential in unstirred solution. The latter technique has been employed in drawing a calibration linear plot. In particular, the performances of the developed electrode system have been compared with those of both pure gold and pure graphene electrode materials. The bi-component electrode was more sensitive; co-catalytic action by the combination of the two components is hypothesised. The system is stable over many potential cycles, as checked by surface-enhanced Raman spectra recorded over time

Efficient hydrogen peroxide generation using reduced graphene oxide-based oxygen reduction electrocatalysts

Electrochemical oxygen reduction has garnered attention as an emerging alternative to the traditional anthraquinone oxidation process to enable the distributed production of hydrogen peroxide. Here, we demonstrate a selective and efficient non-precious electrocatalyst, prepared through an easily scalable mild thermal reduction of graphene oxide, to form hydrogen peroxide from oxygen. During oxygen reduction, certain variants of the mildly reduced graphene oxide electrocatalyst exhibit highly selective and stable peroxide formation activity at low overpotentials (<10 mV) under basic conditions, exceeding the performance of current state-of-the-art alkaline catalysts. Spectroscopic structural characterization and in situ Raman spectroelectrochemistry provide strong evidence that sp 2-hybridized carbon near-ring ether defects along sheet edges are the most active sites for peroxide production, providing new insight into the electrocatalytic design of carbon-based materials for effective peroxide production

Electrochemical and nanogravimetric studies of iron phthalocyanine microparticles immobilized on gold in acidic and neutral media

An electrochemical quartz crystal nanobalance has been used to study the redox behavior of iron phthalocyanine (FePc) microparticles attached to gold in contact with acidic and neutral aqueous solutions at different pH values in the absence and presence of oxygen, respectively. Five redox transformations have been detected: one has been assigned to the Fe2+/Fe3+ redox process, while four of those have been assigned to the oxidation and reduction of the Pc ring; however, the reduction of Fe2+ and the reoxidation of Fe+ cannot be entirely excluded at potentials more negative than ca. −0.4 V vs. saturated calomel electrode (SCE). The redox processes are accompanied with significant mass changes which are related to the sorption and desorption of counterions and solvent molecules. An extensive solvent swelling occurs. The relatively slow motion of solvent molecules introduces a substantial scan rate dependence regarding the mass change during potential cycling. Due to the participation of H+ ions, the processes related to the oxidation and reduction of the Pc ring show pH dependence. Simultaneous with the charge transfer processes, solid-solid phase transitions can be assumed, especially in the case of the redox transformations occurring at most cathodic potentials. The mass change that can be detected in the presence of oxygen indicates a bonding of oxygen to FePc. During a cathodic voltammetric scan, the reduction of oxygen (ORR) starts when the central iron (III) ion of FePc is converted to Fe(II) during reduction. It follows that the electrocatalytic efficiency of FePc, which is comparable with that of Pt in acid and neutral solutions, cannot be expected at even lower overpotentials because the redox transformation of the central Fe ion of FePc determines the rate of the ORR