In-situ laser Raman spectroscopy of nickel oxide supported on. gamma. -Al/sub 2/O/sub 3/

Recent in situ laser Raman spectroscopy (LRS) studies revealed that crystalline oxides (3-dimensional oxide phases) and supported metal oxides (2-dimensional oxide phases) exhibit different responses to thermal treatments in a controlled environment of dry air. For crystalline oxides the thermal treatment is reversible and only thermal broadening of the metal-oxygen Raman bands are observed at elevated temperatures. The supported metal oxides previously examined for the effect of water vapor upon the Raman bands are tungsten oxide, molybdenum oxide, vanadium oxide, rhenium oxide, and chromium oxide. In these Raman studies the metal oxides were supported on ..gamma..-Al/sub 2/O/sub 3/ and TiO/sub 2/. All of these supported metal oxides exhibit strong Raman bands at 900-1100 cm/sup -1/ which have been assigned to the symmetric stretch of the terminal M=O bonds. Another common feature of the supported metal oxides listed above is that they all possess high oxidation states when oxidized (Mo/sup 6 +/, V/sup 5 +/, Re/sup 7 +/, and Cr/sup 6 +/). There is no in-situ Raman data in the literature about supported metal oxides on ..gamma..-Al/sub 2/O/sub 3/ and TiO/sub 2/ that possess low oxidation states (Ni/sup 2 +/, Cu/sup 2 +/, and Co/sup 2 +/). In the present studymore » the authors report the first in-situ laser Raman data for nickel oxide supported on ..gamma..-Al/sub 2/O/sub 3/. 17 references.« less