Potassium-Selective Solid-Contact Electrode with High-Capacitance Hydrous Iridium Dioxide in the Transduction Layer

This work presents new material for solid-contact layers—hydrous iridium dioxide IrO2·2H2O, characterized by high electrical capacitance value, evaluated using chronopotentiometry (1.22 mF) and electrochemical impedance spectroscopy (1.57 mF). The remarkable electrical parameters of layers resulted in great analytical parameters of IrO2·2H2O-contacted potassium-selective electrodes. Various parameters of ion-selective electrodes were examined in the scope of this work using a potentiometry method including: linear range, repeatability, stability of potentiometric response and sensitivity to varying measurement conditions. The analytical parameters obtained for solid-contact electrodes were compared with the ones obtained for coated disc electrodes to evaluate the influence of the iridium dioxide layer. The linear range of the IrO2·2H2O-contacted K+-selective electrodes covered concentrations of K+ ions from 10−6 to 10−1 M and the potential stability was estimated at 0.097 mV/h. The IrO2·2H2O-contacted electrodes turned out to be insensitive to varying light exposure and changes in the pH values of measured solutions (in the pH range of 2 to 10.5). A water layer test proved that, contrary to the coated disc electrode, the substantial water film is not formed between the ion-selective membrane and iridium dioxide layer.

Synthesis and Characterization of 3-DOM IrO2 Electrocatalysts Templated by PMMA for Oxygen Evolution Reaction

Three-dimensional ordered macroporous (3-DOM) IrO2 material was prepared using PMMA as a template and ammonia as a chelator. These 3-DOM IrO2 honeycomb arrays showed a large surface area and ordered macropores (155 nm in diameter) cross-linked by secondary mesopores. Internal structures of 3-DOM IrO2 material were observed microscopically through these secondary pores. According to the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) spectra, 3-DOM IrO2 has a rutile crystal structure and is mainly composed of iridium dioxide. In acidic electrolytes, the overpotential of 3-DOM IrO2 material at 0.5 mV cm−2 was only 0.22 V. Accelerated durability tests demonstrated excellent durability of 3-DOM IrO2 as an oxygen evolution reaction (OER) catalyst.

Surface Characteristics of Ti/IrO2 Anode Material and its Electrocatalytic Properties for Polycyclic Aromatic Hydrocarbons (PAHs) Degradation in Aqueous Solution

In this study, electrochemical degradation of 16 priority PAHs was examined using Ti/IrO2 anode. Iridium dioxide (IrO2) was coated by thermal decomposition of appropriate precursor solution on surface of titanium plate. Surface morphology of coated surface was observed by FESEM and XRD analysis. All electrochemical experiments were conducted using synthetic solution of PAHs in a batch cell under galvanostatic condition. GC-MS was used to quantify PAHs concentration. Electrochemical oxidation results reveal significant degradation of PAHs at Ti/IrO2 surface. Total PAHs removal was about 97 % at all studied initial pH values 3, 6 and 9 in the presence of electrolyte. Crystalline surface of Ti/IrO2 anode exhibited good electrocatalytic properties towards PAHs degradation.

The Electrochemical Characterization of Electrochemically Synthesized MnO2-Based Mixed Oxides for Supercapacitor Applications

Nanostructured elements, including: manganese-molybdenum (Mn-Mo) oxide, manganese-molybdenum-tungsten (Mn-Mo-W) oxide, manganese-molybdenum-iron (Mn-Mo-Fe) oxide, manganese-molybdenum-cobalt (Mn-Mo-Co) oxide, manganese-vanadium-tungsten (Mn-V-W) oxide, manganese-vanadium-iron (Mn-V-Fe) oxide and manganese-iron (Mn-Fe) oxide, have been anodically deposited onto titanium substrates by employing an iridium dioxide interlayer (Ti/IrO2anode). The electrochemical characteristics of the resultant oxide deposits have been investigated by cyclic voltammetry (CV) in an aqueous 0.1 M Na2SO4solution. The voltammetric behaviors of the oxide deposits observed are significantly influenced by the doped elements. Molybdenum doping is found to be advantageous at improving the capacitance characteristics of anodically deposited manganese oxide. Comparatively, iron and vanadium doping are found to be unfavorable. The structure and crystallinity of these deposits have been identified by X-ray diffraction (XRD). The surface morphologies of these oxides were acquired from field emission scanning electron microscopes (FESEM). The high values of electrical parameters for the doped deposits are attributed to the net-like and sponge-like nanostructure, and low crystallinity of the doped manganese oxides. The deposit of Mn-Mo oxides exhibits an excellent capacitive-like behavior, possessing the maximum specific capacitance of 810 F g-1at a CV scan rate of 5 mV s-1in aqueous 0.1 M Na2SO4solution.