Zinc(II) and Manganese(II) Oxalatopalladates as Precursors of Bimetallic Nanomaterials
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Zinc(II) and Manganese(II) Oxalatopalladates as Precursors of Bimetallic Nanomaterials I. A. Garkul’a, *, A. V. Zadesenetsa, P. E. Plyusnina, E. Yu. Filatova, T. I. Asanovaa, D. V. Kozlovb, and S. V. Koreneva aNikolaev
Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia *e-mail: [email protected]
b
Received April 14, 2020; revised May 19, 2020; accepted May 27, 2020
Abstract—The thermal properties of [{Zn(H2O)3(PdOx2)}2(μ-H2O)2] · 4H2O and {(μ-Ox)Pd(μ-Ox)Mn(H2O)3}n · nH2O have been studied in various atmospheres. Zinc forms the intermetallide ZnPd in inert (He) and reductive (H2) atmospheres and a ZnO–PdO oxide mixture in an oxidative (air) atmosphere. Manganese forms MnO–Pd mixtures in an inert atmosphere, experiences deeper oxidation to Mn3O4 in an oxidative atmosphere, and is partially reduced to form the intermetallide Mn3Pd5 in a reductive atmosphere. High catalytic activity in CO photooxidation has been discovered in the Zn-containing sample deposited onto a TiO2 substrate. The XAFS spectroscopy data for the model catalysts make it possible to assume the formation of nanosized palladium particles during the hydrogen reduction of supported precursors. Keywords: palladium, thermogravimetry, photocatalysis, EXAFS DOI: 10.1134/S003602362010006X
INTRODUCTION Noble metals are of great importance in the development of contemporary industry; it is impossible to imagine such branches as electronics [1], medicine [2–5], and chemical production without their application. Noble metals play an important part in catalysis. They are used in hydrogenation [6, 7] and CO capture and oxidation [8, 9], cross-coupling reactions [10, 11], and in many other catalytic processes. Functional materials based on noble metals are in demand, and their synthesis is a topical problem of contemporary chemistry. Particular attention should be paid to the bimetallic systems formed by noble and nonprecious metals, as their mutual effect improves the overall catalytic activity in comparison with monometallic analogues [12]. The synthesis of such functional materials is attended with some difficulties associated with the sizes and homogeneity of particles, the stoichiometry of metals, and the deposition of nanoalloys onto catalytic supports. One of the very efficient solutions that make it possible to manage all the listed problems is to use coordination compounds, in which the cationic and anionic spheres are formed by corresponding metals. In most cases, such compounds can be classified with double complex salts (DCSs) on the condition that the cation and the anion are discrete with respect to each other; however, this is not observed for the precursors discussed in this paper despite their for-
mal similarity to DCSs. Our choice caused by that the metals in such precursors are already mixed with each other, thus facilitating the attainment of a single-phase sta
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