Electrodeposition of lead dioxide on titanium substrate

Modern technology causes the renewal of the interest to physical and chemical properties of solid oxide electrodes. Among these, PbO2/substrate has attracted considerable attention due to its application as an electrode in backup current sources. It was shown that the stable and active lead dioxide coating can be produced by appropriate pretreatment of the titanium substrate, including the coating of the substrate with colloidal graphite.

THE STUDY ON SOME PARAMETERS AFFECTING THE DEGRADATION OF METHYLENE BLUE IN WATER BY ELECTRO-FENTON USING TI/PBO2 ANODE

In this work, the combination of two advanced oxidation processes, electro-Fenton (hydroxyl radical ●OH generated by reactions on cathode) and anodic oxidation (●OH produced directly on anode), in the same reactor was studied to evaluate the treatment of methylene blue (MB) dye in aqueous solutions. This electrochemical system was equipped with a commercial carbon felt cathode (9.5cm 12cm), lead dioxide-coated titanium anode (10 12cm), direct current (DC) and continuously aerated. The effects of operating parameters such as pH, applied current (I), catalyst concentration ([Fe2+]) and MB concentration (C0) on MB removal efficiency were investigated through monitoring MB concentration at different times by spectrophotometric method. An optimal process was achieved at the condition of [Fe2+] = 0.1 mM; pH 3.0; [Na2SO4] = 0.05 M; i = 2.5 mA.cm-2 and after 60 minutes of electrolysis, 92.19% of MB was removed which was far higher than the figure obtained by using individually electro-Fenton (73.77%) or anodic oxidation (58.04%). These experimental results have demonstrated that the combination of electro-Fenton and anodic oxidation using Ti/PbO2 electrode is a prospective method for destruction of persistent dyes.

Electrosynthesis and characterization of lead dioxide–perfluorobutanesulfonate composite

The effect of potassium perfluorobutanesulfonate on the kinetic features of electrodeposition of lead dioxide from methanesulfonate electrolytes has been investigated. The introduction of C4F9SO3K into the lead dioxide deposition electrolyte leads to insignificant inhibition of the Pb2+ electrooxidation process, while the mechanism of the process does not change. A composite coating is formed upon deposition of coatings from electrolytes containing surfactants. The surface of a composite material consists of a mixture of clearly expressed large crystalline blocks with sharp angles and small crystals. Energy dispersive X-ray analysis revealed the satisfactory distribution of modifying elements in the entire sample bulk, and not only on the coating surface. It was shown that the electrocatalytic activity of lead dioxide–perfluorobuthanesulfonate composite differs from the undoped sample. The oxygen evolution reaction slightly decelerates on a PbO2–C4F9SO3K composite. The Tafel slopes in 1 M HClO4 calculated from these curves plotted in semilogarithmic coordinates are 136 and 145 mV dec–1 for undoped sample and lead dioxide-surfactant composite, respectively. The reaction of electrochemical oxidation of p-chlorophenol is characterized by the pseudo-first order kinetics with respect to the initial compound. The use of doped C4F9SO3K lead dioxide as an anode leads to the inhibition of the process of oxygen evolution and an almost one and a half higher rate of electrochemical conversion of 4-chlorophenol to aliphatic compounds.

The influence of ultrasound on nucleation in electrodeposition of lead dioxide on a nickel substrate

The effect of ultrasound on the electrodeposition of lead dioxide from lead (II) nitrate on a nickel substrate was studied. It was shown that the highest electrochemical characteristics are observed for the prototypes of backup power sources based on the Pb/HClO4/PbO2 system, in which lead dioxide obtained by electrodeposition under the influence of an ultrasonic field on a nickel substrate was used.

Stable Bicyclic Functionalized Nitroxides: The Synthesis of Derivatives of Aza-nortropinone–5-Methyl-3-oxo-6,8-diazabicyclo[3.2.1]-6-octene 8-oxyls

In recent decades, bicyclic nitroxyl radicals have caught chemists’ attention as selective catalysts for the oxidation of alcohols and amines and as additives and mediators in directed C-H oxidative transformations. In this regard, the design and development of synthetic approaches to new functional bicyclic nitroxides is a relevant and important issue. It has been reported that imidazo[1,2-b]isoxazoles formed during the condensation of acetylacetone with 2-hydroxyaminooximes having a secondary hydroxyamino group are recyclized under mild basic catalyzed conditions to 8-hydroxy-5-methyl-3-oxo-6,8-diazabicyclo[3.2.1]-6-octenes. The latter, containing a sterically hindered cyclic N-hydroxy group, upon oxidation with lead dioxide in acetone, virtually quantitatively form stable nitroxyl bicyclic radicals of a new class, which are derivatives of both 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (TEMPON) and 3-imidazolines.