Search

The nanoscale Co–Mg–O oxide sample (15 wt% in terms of Co 3 O 4) was prepared from the corresponding xerogel synthesized by the modified sol-gel method. The hydrolysis of as-prepared Mg(OCH 3) 2 was carried out using the aqueous solution of Co(NO 3) 2 precursor. The CoO x nanocrystallites of about 10–20 nm in size were shown to be uniformly distributed within the MgO matrix. The reduction of Co–Mg–O in H 2 flow was found to proceed in two separate stages within the temperature ranges of 200–350 °C and 350–600 °C. The prepared binary Co–Mg–O system was demonstrated to possess completely reproducible reduction behavior in the consecutive reduction/reoxidation cycles. The phase composition of the sample exposed to both the reducing and oxidative environment was followed by an in situ X-ray diffraction analysis performed at temperatures of 25, 300, 500 and 700 °C. The determined lattice parameters for MgO (a = 4.219 Å) and Co 3 O 4 (a = 8.110 Å) were found to be slightly increased as compared with the values from Powder Diffraction File, so that the formation of joint non-stoichiometric (Mg 1-x Co x)O and (Co 3-x Mg x)O 4 phases was suggested. The strong chemical interaction of cobalt oxide with MgO matrix was also evidenced by the data of a diffuse reflectance UV–vis spectroscopy. Image 1 • The nanoscale Co–Mg–O oxide system was prepared by the modified sol-gel method. • CoO x species of 10–20 nm in size are uniformly distributed within the MgO matrix. • The prepared Co–Mg–O system possesses completely reproducible reduction behavior. • Strong interaction between Co and Mg oxides was proved by DR UV–vis spectroscopy. [ABSTRACT FROM AUTHOR]