Sol-gel prepared active ternary oxide coating on titanium in cathodic protection

Evaluating the Effect of WO3 on Electrochemical and Corrosion Properties of TiO2-RuO2-Coated Titanium Anodes with Low Content of RuO2

The electrochemical and corrosion characterization of Ti0.97Ru0.03O2/Ti electrodes modified with WO3 was reported. Modification of Ti0.97Ru0.03O2/Ti electrodes with WO3 was previously described as improving the effectiveness of an azo dye degradation in a photoelectrochemical treatment. Thus, the effect of WO3 introduction to oxide film on electrode surface on electrochemical behaviour and stability of the modified electrodes was investigated. Moreover, corrosion behaviour of Ti0.97Ru0.03O2/Ti electrodes modified with WO3 was evaluated with the application of potentiodynamic polarization sweep method and open circuit potential measurement. Electrodes modified with WO3 revealed higher anodic and cathodic peak currents in K4[Fe(CN)6] solution (by 35% for 6%WO3 content) indicating higher electroactive surface area and faster electron transfer reaction. An increase in WO3 amount in the oxide layer caused an increase in the number of active sites determined in Na2SO4 and most of them (more than 80%) were located in the outer and more accessible surface. The investigation of the tested electrodes at high potentials at which oxygen evolution is observed, allowed their classification in the following order showing an increase in their activity towards oxygen evolution reaction: Ti0.97Ru0.03O2/Ti < Ti0.94Ru0.03O2-W0.03O3/Ti < Ti0.91Ru0.03O2-W0.06O3/Ti. Although the electrode modification with WO3 resulted in lower resistance to corrosion in Na2SO4 solution regarding corrosion potential, corrosion current densities were clearly lower in comparison with the non-modified electrode, especially after longer immersion in the solution. ASTs showed that even a small addition of WO3 increased the lifetime of the electrodes. The Ti0.97Ru0.03O2/Ti electrode modification with WO3 seemed to be advantageous for their application in electrochemical and photoelectrochemical degradation of organic pollutants.

Comparative Study between NiCoB and IrO2-Ta2O5/Ti Anodes for Application in Impressed Current Cathodic Protection (ICCP)

In an impressed current cathodic protection system (ICCP) to protect structures against corrosion, the efficient operation depends on the proper selection of the electrodes, particularly the anode, chosen considering the structure to be protected and the environment in which it is located. The nature and overpotential of the anodic reaction determine the operation costs of an ICCP system so that proper anode selection is critically important for an ICCP system to function efficiently. Commercial anodes based on titanium substrates coated with iridium–tantalum oxide mixtures (IrO2-Ta2O5/Ti) are frequently used for this purpose due to low operating overpotentials. However, the gradual passivation of its surface limits its useful life and increases its operating costs, so it is necessary to seek competitive alternatives for its replacement. This study aimed to determine the feasibility of using carbon steel substrates coated with nickel/cobalt/boron (NiCoB/CS) as a viable low-cost alternative to replace IrO2-Ta2O5/Ti anodes in ICCP systems. Comparison between the electrochemical behavior and the corrosion resistance of both types of electrodes shows that the NiCoB/CS anode shows a good electrocatalytic activity and a higher corrosion resistance than IrO2-Ta2O5/Ti coated anodes, indicating that the NiCoB/CS anodes are promising low-cost candidates for ICCP systems.

The investigation of the electrocatalytic and corrosion behavior of a TiO2–RuO2 anode modified by graphene oxide and reduced graphene oxide nanosheets via a sol–gel method

The participation of GO in the coating structure improved the ClER activity, selectivity, and the electrochemical stability of the electrodes significantly.

Metal oxide-coated anodes in wastewater treatment

Electrochemical oxidation is an effective wastewater treatment method. Metal oxide-coated substrates are commonly used as anodes in this process. This article compiles the developments in the fabrication, application, and performance of metal oxide anodes in wastewater treatment. It summarizes the preparative methods and mechanism of oxidation of organics on the metal oxide anodes. The discussion is focused on the application of SnO2, PbO2, IrO2, and RuO2 metal oxide anodes and their effectiveness in wastewater treatment process.

Differences in the electrochemical behavior of ruthenium and iridium oxide in electrocatalytic coatings of activated titanium anodes prepared by the sol-gel procedure

The electrochemical characteristics of Ti0.6Ir0.4O2/Ti and Ti0.6Ru0.4O2/Ti anodes prepared by the sol-gel procedure from the corresponding oxide sols, obtained by force hydrolysis of the corresponding metal chlorides, were compared. The voltammetric properties in H2SO4 solution indicate that Ti0.6Ir0.4O2/Ti has more pronounced pseudocapacitive characteristics, caused by proton-assisted, solid state surface redox transitions of the oxide. At potentials negative to 0.0 VSCE, this electrode is of poor conductivity and activity, while the voltammetric behavior of the Ti0.6Ru0.4O2/Ti electrode is governed by proton injection/ejection into the oxide structure. The Ti0.6Ir0.4O2/Ti electrode had a higher electrocatalytical activity for oxygen evolution, while the investigated anodes were of similar activity for chlorine evolution. The potential dependence of the impedance characteristics showed that the Ti0.6Ru0.4O2/Ti electrode behaved like a capacitor over a wider potential range than the Ti0.6Ir0.4O2/Ti electrode, with fully-developed pseudocapacitive properties at potentials positive to 0.60 VSCE. However, the impedance characteristics of the Ti0.6Ir0.4O2/Ti electrode changed with increasing potential from resistor-like to capacitor-like behavior.

Photoelectrochemical properties of sol-gel obtained titanium oxide

The photoelectrochemical properties of a sol-gel prepared titanium oxide coating applied onto a Ti substrate were investigated. The oxide coating was formed from an inorganic sol thermally treated in air at 350?C. The coating consisted of agglomerates of narrow size distribution around 100 nm. The photoelectrochemical characteristics were evaluated by investigating the changes in the open circuit potential, current transients and impedance characteristics of a Ti/TiO2 electrode upon illumination by UV light in H2SO4 solution and in the oxidation of benzyl alcohol. The electrode was found to be active for photoelectrochemical reactions in the investigated solutions.

Electrocatalytic properties and stability of titanium anodes activated by the inorganic sol-gel procedure

The properties of activated titanium anodes, RuO2-TiO2/Ti and RuO2--TiO2-IrO2/Ti, prepared from oxide sols by the sol-gel procedure, are reviewed. RuO2 and TiO2 sols were synthesized by forced hydrolysis of the corresponding chlorides in acid medium. The morphology of the prepared sols was investigated by transmission electron microscopy. The chemical composition of the RuO2 sol was determined by X-ray diffraction and thermogravimetric analysis. The loss of electrocatalytic activity of a RuO2-TiO2/Ti anode during an accelerated stability test was investigated by examination of the changes in the electrochemical characteristics in the potential region of the chlorine and oxygen evolution reaction, as well as on the open circuit potential. These electrochemical characteristics were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and polarization measurements. The changes in electrochemical characteristics of the anode prepared by the sol-gel procedure were compared to the changes registered for an anode prepared by the traditional thermal decomposition of metal chlorides. The comparison indicated that the main cause for the activity loss of the sol-gel prepared anode was the electrochemical dissolution of RuO2, while in the case of thermally prepared anode the loss was mainly caused by the formation of an insulating TiO2 layer in the coating/Ti substrate interphase. The results of an accelerated stability test on RuO2-TiO2/Ti and RuO2--TiO2-IrO2/Ti anodes showed that the ternary coating is considerably more stable than the binary one, which is the consequence of the greater stability of IrO2 in comparison to RuO2.

Supercapacitive characteristics of electrochemically active porous materials

The results of an investigation of the capacitive characteristics of sol-gel-processed titanium- and carbon-supported electrochemically active noble metal oxides, as representatives of porous electrode materials, are presented in the lecture. The capacitive properties of these materials were correlated to their composition, the preparation conditions of the oxides and coatings, the properties of the carbon support and to the composition of the electrolyte. The results of the electrochemical test methods, cyclic voltammetry and electrochemical impedance spectroscopy, were employed to resolve the possible physical structures of the mentioned porous materials, which are governed by the controlled conditions of the preparation of the oxide by the sol-gel process.