L. E. Derlyukova

The effect of Fe2O3 dopants on electrophysical and sorption properties of ZnO

The effect of Fe2O3 dopants (0–0.8 mol.%) on ZnO conductivity and its chlorine chemisorption ability has been studied in the temperature range of 20–250 °C. Introduction of dopants increases the activation energy of ZnO conductivity and decreases the conductivity. The effective charge of the chemisorbed chlorine species as well as the strength of their bonding to the surface in samples containing Fe2O3 are considerably lower than in initial ZnO, which leads to a decrease of reactivity of the doped catalysts in chlorination.

Chemisorption of hydrogen sulfide on lead sulfide

The hydrogen sulfide chemisorption on lead sulfide at 22–100°C is studied by static testing in a vacuum and by pulsed chromatography. It is established that H2S is sorbed in reversible and irreversible forms and that the process is accompanied by the sample charging. Irreversibly sorbed hydrogen sulfide is removed by heating the sample in a vacuum or in an inert-gas stream at temperatures exceeding the adsorption temperature by 30–50°C.

Oxidizing catalysts supported on nanostructured TiO2

This paper compares the catalytic performance of platinum catalysts supported on different forms of TiO2. A composite material in the form of Pt supported on titanium dioxide nanotubes is shown to possess the highest catalytic performance for CO oxidation. It exhibits stable catalytic activity at temperatures from 65 to 300°C.

The effect of platinum on the SnO2 sorption properties

Chemisorption of SO2 and O2 at Pt-modified SnO2 is studied by using the vacuum static method, with simultaneous recording of electrical conductivity, over the 22 to 300°C temperature range. The SnO2 surface modification results in the increasing of SO2 adsorption and weakening of the gas-surface bonding. The chemisorption enhances the samples’ electrical conductivity. The surface pretreatment with oxygen leads to the decreasing of the successive SO2 chemisorption.

Effect of SO2 on chlorination of Bi2O3 + Fe2O3 mixtures

The reaction of Bi2O3 + Fe2O3 mixtures with chlorine and SO2 at 250–700°C is studied. At 300–500°C, the degree of bismuth chloride sublimation from the oxide mixture increases in the presence of SO2. Chemical sublimation of FeCl3 occurs after BiCl3 is virtually completely recovered from the solid phase.

Sorptive properties of antimony-doped In2O3

O2, Cl2, and SO2 chemisorption on the surface of nanocrystalline In2O3 doped with antimony (0.2 and 2.7 at %) has been studied at temperatures from 22 to 200°C. The results indicate that antimony prevents the formation of nonconducting indium chlorides on the surface of nanocrystalline In2O3 during Cl2 chemisorption. The logarithm of the conductivity of Sb-doped In2O3 is a nearly linear function of the surface coverage with chlorine, which makes it a candidate chlorine-sensing material. At the same time, antimony doping reduces the SO2 response of In2O3.

Investigation of chemisorption properties of the PbO surface

Chemisorption of O2, Cl2, and SO2on the orthorhombic and tetragonal PbO samples was studied in the 225—550 °C temperature range. The main features of chemisorption are independent of the crystal modification of the sample. The change in the type of conductivity of PbO during chemisorption of O2was found.

Effect of gallium oxide dopants on electrophysical and sorption properties of zinc oxide

The effects of lithium oxide dopants (0.5–0.8 at. % Li) on the electrophysical and sorption properties of ZnO were studied in the temperature range from 150 °C to 410 °C. The introduction of lithium increases the activation energy of the conductivity of ZnO, decreases its conductivity, and increases the amount of S02 sorbed. Two forms of chemisorbed SO2 (donor and acceptor) are observed on the surface.

Physicochemical and functional properties of modified tin dioxide

Specimens of tin dioxide with modifying Sb and Pt additives are synthesized. Their physicochemical properties (specific surface area, porosity, and conductivity), chemisorption and catalytic activity in the model reaction of CO oxidation are studied. A considerable chemisorption of CO on SnO2 and SnO2-SbOx is observed at 150–180°C. The oxidation of CO in the flow of gases starts in the same temperature range. An addition of platinum leads to a significant increase in the rate of CO oxidation, the reaction starts at 80°C. It is proposed that the process proceeds at the SnO2/Pt interface.

Determination of chlorine in air using ZnO modified with gallium and indium oxides

We examine the possibility of detecting Cl2 in flowing air at temperatures from 150 to 350°C using polycrystalline ZnO containing additions of gallium and indium oxides. ZnO modified with gallium via impregnation has a fast, stable, well-reproducible response and a short relaxation time. Its response passes through a maximum at 250°C. The interaction is not complicated by formation of chlorination products. In the range 5−500 ppm, its resistance is a linear function of the square root of Cl2 concentration.