Nanocomposites and nanomaterials

Electrophysical and catalytic properties 
of the Bi2Sr2-xNdxCaCu2Oy (0 ≤ x ≤ 0.1) cuprates 
O.Z. Didenko1, G.R. Kosmambetova1, I.V. Fesych2, D.D. Naumova2, T.A. Voitenko2, S.A. Nedilko2, P.E. Strizhak1 
1 L.V. Pysarzhevsky Institute of Physical Chemistry of the NAS of Ukraine.
Prospect Nauky, 31, Kyiv-03028, Ukraine.
E-mail: o.z.didenko@gmail.com
2 Taras Shevchenko National University of Kyiv.
Volodymyrska St., 60, Kyiv-01033, Ukraine.

The complex Nd-doped cuprates of bismuth Bi2Sr2-xNdxCaCu2Oy, where the degree of substitution of strontium by neodymium x = 0, 0.05, and 0.1, were synthesized by a two-step processing technique with precursor preliminary preparation. The structural, textural, electrophysical characteristics and catalytic properties in the carbon monoxide oxidation reaction were studied.
We found that replacing the divalent Sr ion with the trivalent rare-earth Nd ion in Bi2Sr2-xNdxCaCu2Oy with a variable degree of substitution is accompanied by a change in a number of characteristics. According to X-ray diffraction (XRD) analysis, the synthesized samples based on Bi-containing cuprates are homophasic and correspond to the Bi-2212 phase. An increase in the neodymium content leads to an antibatical change in the unit cell parameters of the prepared cuprates. Parameter c decreases while parameter a and volume of the unit cell increase. Also, XRD analysis showed a slight decrease in the value of the X-ray density with an increase in the degree of substitution of Sr by Nd. An increase in the specific surface area determined using the BET method and the oxygen index calculated from the iodometric titration are observed with an increase in x from 0 to 0.1. 
The catalytic properties were investigated in the CO oxidation with oxygen using the flow method with gas chromatographic analysis of the components and reaction products at the reactor outlet. The catalytic activity of the Nd-doped cuprates increases almost three times in comparison with the activity of an unsubstituted sample.
Thus, an increase in the degree of substitution of strontium with neodymium in a Bi-2212 cuprate leads to an increase in structural and textural defects, an increase in the amount and mobility of oxygen in the crystal lattice, and, as a result, to an increase in catalytic activity in the CO oxidation reaction.