Activation of carbon tow electrodes for use in iron aqueous redox systems for electrochemical applications

Excellent chemical inertness, good conductivity and high overpotentials for water electrolysis make carbon fibres (CFS) an ideal electrode material for electrochemical applications. A customized design of three-dimensional (3D) carbon electrodes can be achieved by tailored fibre placement of carbon tows with textile production techniques like embroidery. After manufacturing of the 3D structure, appropriate removal of the polymer coating and oxidative activation is required to achieve low overpotentials and avoid thermal treatments of the carbon structure. For the electrolytes Na[FeIII-racEDDHA] and K4[FeII(CN)6] a sequential treatment by acetone extraction and anodic oxidation was identified to yield optimum surface activation. Electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy of activated fibres indicated complete removal of the coating layer without damage of the CFS. From electrochemical impedance spectroscopy (EIS) at the carbon tow electrodes, charge transfer resistances of <0.1 Ω (0.023 Ω g) and < 0.2 Ω (0.046 Ω g) were determined at 50% state-of-charge (SoC) for 65 mM K4[FeII(CN)6] and 65 mM Na[FeIII-racEDDHA], respectively. In potentiostatic bulk electrolysis no electrode deactivation was observed during 10 charge/discharge cycles (5-6 hours) between 10% and 90% SoC. The processing of carbon tows by textile techniques to near net shaped 3D electrodes opens a new method to manufacture electrodes for electrochemical applications, such as redox flow cells.Peer reviewe

Reactive metal-support interaction in the Cu-In2O3 system: intermetallic compound formation and its consequences for CO2-selective methanol steam reforming

The reactive metal-support interaction in the Cu-In2O3 system and its implications on the CO2 selectivity in methanol steam reforming (MSR) have been assessed using nanosized Cu particles on a powdered cubic In2O3 support. Reduction in hydrogen at 300 °C resulted in the formation of metallic Cu particles on In2O3. This system already represents a highly CO2-selective MSR catalyst with ~93% selectivity, but only 56% methanol conversion and a maximum H2 formation rate of 1.3 µmol gCu−1 s−1. After reduction at 400 °C, the system enters an In2O3-supported intermetallic compound state with Cu2In as the majority phase. Cu2In exhibits markedly different self-activating properties at equally pronounced CO2 selectivities between 92% and 94%. A methanol conversion improvement from roughly 64% to 84% accompanied by an increase in the maximum hydrogen formation rate from 1.8 to 3.8 µmol gCu−1 s−1 has been observed from the first to the fourth consecutive runs. The presented results directly show the prospective properties of a new class of Cu-based intermetallic materials, beneficially combining the MSR properties of the catalyst’s constituents Cu and In2O3. In essence, the results also open up the pathway to in-depth development of potentially CO2-selective bulk intermetallic Cu-In compounds with well-defined stoichiometry in MSR

Reactive metal-support interaction in the Cu-In2O3 system: intermetallic compound formation and its consequences for CO2-selective methanol steam reforming.

The reactive metal-support interaction in the Cu-In2O3 system and its implications on the CO2 selectivity in methanol steam reforming (MSR) have been assessed using nanosized Cu particles on a powdered cubic In2O3 support. Reduction in hydrogen at 300&nbsp;°C resulted in the formation of metallic Cu particles on In2O3. This system already represents a highly CO2-selective MSR catalyst with ~93% selectivity, but only 56% methanol conversion and a maximum H2 formation rate of 1.3&nbsp;µmol gCu -1&nbsp;s-1. After reduction at 400&nbsp;°C, the system enters an In2O3-supported intermetallic compound state with Cu2In as the majority phase. Cu2In exhibits markedly different self-activating properties at equally pronounced CO2 selectivities between 92% and 94%. A methanol conversion improvement from roughly 64% to 84% accompanied by an increase in the maximum hydrogen formation rate from 1.8 to 3.8&nbsp;µmol gCu -1&nbsp;s-1 has been observed from the first to the fourth consecutive runs. The presented results directly show the prospective properties of a new class of Cu-based intermetallic materials, beneficially combining the MSR properties of the catalyst's constituents Cu and In2O3. In essence, the results also open up the pathway to in-depth development of potentially CO2-selective bulk intermetallic Cu-In compounds with well-defined stoichiometry in MSR