A Novel Indium-Induced-Synthesis In0.17Ru0.83O2 Nanoribbon as Highly Active Electrocatalysts for Oxygen Evolution in Acidic Media at High Current Densities above 400 mA cm−2

Ruthenium dioxide-based electrocatalyst possesses the most potential in acidic oxygen evolution reaction (OER), however, most of them show low current density, low mass activity and unsatisfied stability under strong acidic...

THE USE OF RuO DEPOSITED ON HZSM-5 WITH A DIFFERENT SILICATE MODULUS IN THE REACTION OF LEVULINIC ACID HYDROGENATION

В работе проводилось исследование рутений-содержащих катализаторов на основе цеолитов HZSM-5 с различным кремнеземным модулем (40, 80 и 400) в реакции гидрирования левулиновой кислоты (ЛК) до гамма-валеролактона. Была изучена зависимость активности композитов Ru/HZSM-5 от кремнеземного модуля выбранного цеолита и от содержания диоксида рутения на поверхности. Показано, что образец Ru/HZSM-5 с кремнеземным модулем 40 позволяет в достаточно мягких условиях (температура 100С, парциальное давление водорода 1 МПа) достичь 98% конверсии ЛК за 60 мин реакции в водной среде. In this work, the study of ruthenium-containing catalysts based on zeolites of the HZSM-5 type with different silicate modulus (40, 80 and 400) in the reaction of levulinic acid (LA) hydrogenation to gamma-valerolactone was carried out. The dependence of the activity of Ru/HZSM-5 composites on the silicate modulus of the selected zeolite and on the content of ruthenium dioxide on the surface was studied. It is shown that the Ru/HZSM-5 sample with a silicate modulus equal to 40 allows achieving 98% of LA conversion in 60 minutes of the reaction in an aqueous medium under mild conditions (temperature 100°C, 1 MPa of partial hydrogen pressure).

Potentiometric Sensor with High Capacity Composite Composed of Ruthenium Dioxide and Poly(3,4-ethylenedioxythiophene) Polystyrene Sulfonate

This work presents the first-time application of the ruthenium dioxide–poly(3,4-ethylenedioxythiophene) polystyrene sulfonate high-capacity composite material as a mediation layer in potassium selective electrodes, which turned out to significantly enhance the electrical and analytical parameters of the electrodes. The idea was to combine the properties of two different types of materials: a conducting polymer, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, and a metal oxide, ruthenium dioxide, in order to obtain the material for a solid-contact layer of great electrical and physicochemical parameters. The preparation method for composite material proposed in this work is fast and easy. The mediation layer material was examined using a scanning electron microscope and chronopotentiometry in order to confirm that all requirements for mediation layers materials were fulfilled. Ruthenium dioxide–poly(3,4-ethylenedioxythiophene) polystyrene sulfonate nancomposite material turned out to exhibit remarkably high electrical capacitance (of approximately 17.5 mF), which ensured great performance of designed K+-selective sensors. Electrodes of electrical capacity equal to 7.2 mF turned out to exhibit fast and stable (with only 0.077 mV potential change per hour) potentiometric responses in the wide range of potassium ion concentrations (10−6 M to 10−1 M). The electrical capacity of ruthenium dioxide–poly(3,4-ethylenedioxythiophene) polystyrene sulfonate-contacted electrodes characterized by electrical capacitance parameters was the highest reported so far for this type of sensor.

High Capacity Nanocomposite Layers Based on Nanoparticles of Carbon Materials and Ruthenium Dioxide for Potassium Sensitive Electrode

This work presents the new concept of designing ion-selective electrodes based on the use of new composite materials consisting of carbon nanomaterials and ruthenium dioxide. Using two different materials varying in microstructure and properties, we could obtain one material for the mediation layer that adopted features coming of both components. Ruthenium dioxide characterized by high electrical capacity and mixed electronic-ionic transduction and nano-metric carbon materials were reportedly proved to improve the properties of ion-selective electrodes. Initially, only the materials and then the final electrodes were tested in the scope of the presented work, using scanning and transmission electron microscope, contact angle microscope, and various electrochemical techniques, including electrochemical impedance spectroscopy and chronopotentiometry. The obtained results confirmed beneficial influence of the designed nanocomposites on the ion-selective electrodes’ properties. Nanosized structure, high capacity (characterized by the electrical capacitance value from approximately 5.5 mF for GR + RuO2 and CB + RuO2, up to 14 mF for NT + RuO2) and low hydrophilicity (represented by the contact angle from 60° for GR+RuO2, 80° for CB+RuO2, and up to 100° for NT + RuO2) of the mediation layer materials, allowed us to obtain water layer-free potassium-selective electrodes, characterized by rapid and stable potentiometric response in a wide range of concentrations-from 10−1 to 10−6 M K+.

Optimization of Ruthenium Dioxide Solid Contact in Ion-Selective Electrodes

Ruthenium dioxide occurs in two morphologically varied structures: anhydrous and hydrous form; both of them were studied in the scope of this work and applied as mediation layers in ion-selective electrodes. The differences between the electrochemical properties of those two materials underlie their diverse structure and hydration properties, which was demonstrated in the paper. One of the main differences is the occurrence of structural water in RuO2•xH2O, which creates a large inner surface available for ion transport and was shown to be a favorable feature in the context of designing potentiometric sensors. Both materials were examined with SEM microscope, X-ray diffractometer, and contact angle microscope, and the results revealed that the hydrous form can be characterized as a porous structure with a smaller crystallite size and more hydrophobic properties contrary to the anhydrous form. Potentiometric and electrochemical tests carried out on designed GCD/RuO2/K+-ISM and GCD/RuO2•xH2O/K+-ISM electrodes proved that the loose porous microstructure with chemically bounded water, which is characteristic for the hydrous form, ensures the high electrical capacitance of electrodes (up to 1.2 mF) with consequently more stable potential (with the potential drift of 0.0015 mV/h) and a faster response (of a few seconds).