Abstract
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).
Highlights
Ruthenium dioxide can be considered as undeniably noteworthy amongst various electroactive materials previously used as mediation layers in solid-contact ion-selective electrodes (ISEs)
All tests including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronopotentiometry (Ch) were conducted in the 3-electrode cell consisting of a working electrode—a glassy carbon disc electrode covered with a RuO2 layer, reference electrode, and auxiliary electrode—a glassy carbon rod
Discussion subjected to tests in order to define their microstructure, wetting properties, crystallite size, and Before examining their suitability as enabled mediation layers, both forms of ruthenium dioxide were thermal behavior
Summary
Ruthenium dioxide can be considered as undeniably noteworthy amongst various electroactive materials previously used as mediation layers in solid-contact ion-selective electrodes (ISEs). Augustyn et al [11] report that the high electrical capacitance and rapid faradaic reaction of RuO2 xH2 O are induced by its unique features, such as rapid electron transport caused by the metallic conductivity of RuO2 , rapid proton transport as a result of the presence of structural water, and the redox behavior of various Ru–RuOx states allowing for faradaic energy storage and a large surface area The differences between both forms of RuO2 (hydrous and anhydrous) used for solid contact layers—those described in the Introduction and those presented in the Materials Characteristic section—have its reflection in the performance of ion-selective electrodes. In order to help scientists who are concerned obtain similar results of capacitance for the ruthenium dioxide layer, in this article, we present a completely optimized procedure for the application of ruthenium oxide layers
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