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A study was made of the electron paramagnetic resonance ͑EPR͒ in electrolytically and chemically prepared manganese dioxides intended for use in power sources. A typical EPR signal for the powdered MnO 2 samples is wide single line with g ϭ 1.94. The replacement of some Mn 4ϩ ions by Mn 3ϩ modified the character of the exchange interaction. A correlation was established between the width of the EPR signal and the ionic conductivity value as well as Mn 3ϩ /Mn 4ϩ ratio and OH Ϫ groups contents in the samples. It is supposed that the EPR data can be useful for the semiquantitative expression of chemical and electrochemical activity of different MnO 2 samples. In some samples EPR signals with g ϭ 2.000, A ϭ 8.81 mT ͑A is hyperfine structure parameter͒ were revealed due to the presence of MnSO 4 water solutions traces.

The influence of dopant ions on the phase composition and structure ordering of electrodeposited nanoxides of manganese was investigated. Additives of dopant ions of Li and Co(II) and fluorine-containing electrolytes have been applied for preparation of samples by anode electrodeposition. The samples have been studied by methods of chemical analysis, XRD, TEM, Fourier spectroscopy etc. TEM observation showed that the presence of dopant ions of lithium and cobalt in electrolyte decreased crystallinity of samples, influenced the length and perfection of nanorods, and made structure more defective. The diametres of the nanorods ranged from 10 to 20 nm

Process of photoelectrocatalytic aminoazodye methyl orange (MO) degradation was studied in a neutral salt electrolyte under UV irradiation with the titanium dioxide photoelectrocatalyst of nanodispersed morphology and anatase structure synthesized by developed by authors technology from metatitanic acid TiO(OH)2 suspension. The activity was also compared with standard samples (P25 with anatase / rutile phase ratio of 80 : 20, pure rutile). The phase composition, unit cell parameters, and dispersion of the samples were determined. The results of thermogravimetric measurements, characteristics of porosity were also analyzed. The presence of Ti 3+ defects for the synthesized sample could be the reason of band gap decrease in this semiconductor to 2.75 eV and growth of MOs anode oxidation currents under UV irradiation at high scan rates (above 50 mV / s) and potentials below 500 mV (CSE) comparing with standard samples. The photoelectrocatalytic activity of samples is defined by nanodispersity, crystallite morphology, pore size distribution, varies symbatically with the concentration of Ti 3+ , surface hydroxide groups. 80 : 20, чистого рутила). Рентгенографічним методом визначені фазовий склад, параметри елементарної комірки, дисперсність зразків. Проаналізовані результати термогравіметричних вимірювань, характеристики поруватості. Показана присутність дефектів Ti 3+ для синтезованого зразка, що може бути причиною зменшення ширини забороненої зони напівпровідника до 2.75 еВ і збільшення струмів анодного окиснення МО в умовах УФ-опромінення при високих швидкостях сканування (від 50 мВ/с) і потенціалах до 500 мВ (ХСЕ) порівняно із стандартними зразками. Фотоелектрокаталітична активність зразків визначається нанодисперсністю, морфологією кристалітів, розподілом пор за розмірами та змінюється симбатно з концентрацією Тi 3+ , поверхневих гідроксильних груп. Ключові слова: діоксид титану; фотоелектрокаталіз; деградація; аміноазобарвник. Анотація Вивчено процес фотоелектрокаталітичної деградації аміноазобарвника метилоранжа (МО) під дією УФопромінення в нейтральному солевому електроліті з використанням каталізатора -титан (IV) оксиду нанодисперсної морфології зі структурою анатаза, синтезованого із суспензії гідратованого титан (IV) оксиду TiO(OH)2. Порівняно активність стандартних зразків (Р25 із співвідношенням фаз анатаз/рутил

Manganese dioxide samples were prepared from fluorine containing electrolytes with additives of Co 2+ ions. Atomic absorption spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis were the methods of the samples characterisation. Manganese dioxide at the presence of cobalt forms nanosized ramsdellite structure crystallites of mostly needle-like morphology with significant content of hydroxide groups. The main phase state in manganese dioxide samples obtained at the presence of cobalt is γ-MnO2 with ramsdellite structure and low content of intergrowth defects. The sample doped both with lithium and cobalt can be indexed to a hollandite-type structure (tetragonal; space group I4/m) of α-MnO2.

The ionic dopant additives have different mechanisms of their influence upon MnO2 electrocrystallisation process and depending on dopants added the following polymorphs are stabilised: α-MnO2 (hollandite, I4/m) -NH + 4 ; γ-MnO2 (ramsdellite, P bnm) -Co 2+ , Fe 2+ ; layered polymorph δ-MnO2 (birnessite, C2/m) -Cr 3+ . The defect states of intergrowth method in ramsdellite matrix and twinning, OH groups studied by X-ray diffraction and the Fourier transform infrared mtehod, respectively, indicate their high content in case of Fe 2+ and Co 2+ -doped manganese dioxide. CVA oxygen reduction reaction peaks were established after experiments in alkaline electrolytes and dioxygen (argon, air) atmosphere. Activity of doped samples studied is comparable with other published data. Both doped with Co 2+ and Fe 2+ samples display maximal currents and some distinctive features in oxygen reduction reaction.

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Manganese dioxide obtained by electrolytic doping technique was subjected to investigations of influence of cationic additives in an electrolyte on defects in structure and prospectives of improvements in its functionality. The Chabre-Pannetier model was used for this purpose. The results indicate on the variability of yI� yla polymorphs intergrowth ratios, and twinning. There is a necessity to expand single phase Chabre-Pannetier model based on ramsdellite structure matrix towards multiphase «open structure» polymorphs that are frequently occurred in electrodeposited samples of manganese dioxide.