ISSN 0018-1439, High Energy Chemistry, 2014, Vol. 48, No. 4, pp. 239–243. © Pleiades Publishing, Ltd., 2014. Original Russian Text © A.A. Garibov, T.N. Agaev, G.T. Imanova, S.Z. Melikova, N.N. Gadzhieva, 2014, published in Khimiya Vysokikh Energii, 2014, Vol. 48, No. 4, pp. 281– 285. 239 The γ-radiolysis of water in the presence of some dispersed metal oxides is currently being a subject of intensive research [1–3]. On the basis of these studies it was revealed that the use of nanopowdered oxides (Al 2 O 3 , TiO 2 , SiO 2 , ZrO 2 , etc.) as catalysts sharply increases the molecular-hydrogen accumulation rate during water radiolysis. The radiation-chemical yield of Н 2 is significantly higher in this case compared with the yields in both homogeneous and heterogeneous processes of Н 2 О decomposition on microsized oxides used as catalysts [4–6]. Of these nanosized oxides, zir- conium dioxide (ZrO 2 ) seems the most interesting and promising, since it is a selective catalyst for radiation- induced heterogeneous processes [5, 6]. The studies cited above were focused mostly on the effect of the dose γ-radiation and the size of nanoparticles on the yield of molecular hydrogen [6]. Different methods were used to identify the mechanism of the radiation- catalytic action of the oxide catalysts in the radiolytic processes of water decomposition [6, 7]. However, these methods do not provide information about cer- tain chemical stages of radiation-induced heteroge- neous processes in nano-oxide systems or the forma- tion of adsorption-active and catalytically active sur- face functional groups. Such information can be obtained by UV–Vis and IR spectroscopy techniques [8]. In particular, the hydroxyl cover and electron- acceptor properties of the surface of nano-ZrO 2 were studied by IR spectroscopy [4]. However, there are no IR data on the radiation-induced heterogeneous pro- cess of water decomposition in the nano-ZrO 2 + Н 2 О system. This paper presents the results of an IR spectro- scopic study of the radiation–thermal decomposition of water in the nano-ZrO 2 + Н 2 О heterogeneous sys- tem at Т = 300–673 K using γ-rays; the study was aimed to reveal the role of intermediate species and identify the behavior of adsorption-active hydroxyl groups in these processes. EXPERIMENTAL Zirconia nanopowders with a particle size of d = 20–30 nm were used. The choice of the size is not accidental, since it is with this particle size of ZrO 2 nanopowders that the water radiolysis process is the most efficient according published data [5]. Prior to adsorption, zirconia samples were subjected to ther- mal treatment in a vacuum at a T = 673 K and a pres- sure of 10 –3 Pa for 120 h to dehydroxylate the surface and remove organic contaminants. The control of the surface purity was performed by following the inten- sity of the IR bands due to water and impurity hydro- carbons. The structure of the nano-ZrO 2 samples was investigated by the X-ray diffraction method with CuKα source on a Bruker D8 Advance XRD instru- ment. It was found that nano-ZrO 2 has the centrosym- metric monoclinic crystal structure with unit cell dimensions of a = 5.313 Å, b = 5.213 Å, c = 5.147 Å, α = 90.00 Å, β = 99.22 Å, γ = 90.00 Å, V = 14070 Å 3 , Z = 4.00. Fourier-transform IR absorption spectra were recorded on a Varian 640-IR FTIR spectrometer in the frequency range of ν = 4000–400 cm –1 at room temperature. To measure the absorption spectra, ZrO 2 nanopowders were compressed into tablets with a IR Spectroscopy Study of the Radiation–Thermal Decomposition of Water on Nanosized Zirconium Dioxide A. A. Garibov, T. N. Agaev, G. T. Imanova, S. Z. Melikova, and N. N. Gadzhieva Institute of Radiation Problems, National Academy of Sciences of Azerbaijan, ul. Vakhabzade 9, Baku, AZ1143 Azerbaijan e-mail: agayevteymur@rambler.ru Received June 18, 2013; in final form, November 08, 2013 Abstract—Radiation–thermal decomposition of water on nanosized ZrO 2 in the temperature range of 300– 673 K has been studied by FTIR spectroscopy. It has been revealed by the X-ray diffraction method that the sample used has the centrsymmetric monoclinic crystal structure. It has been shown that nanosized zirco- nium dioxide adsorbs water on via the molecular and dissociative mechanisms. Intermediate products of the radiation-induced heterogeneous decomposition of water, namely, the molecular oxygen and hydrogen per- oxide radical ions, zirconium hydride, and hydroxyl radicals have been detected. A comparative analysis of changes in the absorption bands of molecular water and surface hydroxyl groups with temperature has been conducted, and the stimulating role of radiation in the radiation–thermal process of water decomposition has been revealed. DOI: 10.1134/S0018143914030059 RADIATION CHEMISTRY