In this work, we coated molybdenum oxide on submicrospheres of amorphous alumina and crystalline alumina, using a sonochemical method. The sonication products were characterized by transmission electron microscopy, x-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, ultraviolet-visible, Raman, Fourier transform infrared spectroscopy, and surface area (Brunauer-Emmett-Teller) measurements. We found that on crystalline alumina, the blue oxide of molybdenum was formed, while on amorphous alumina, the presence of an isolated tetrahedrally coordinated Mo oxide species was confirmed. It seems that the amount and types of surface hydroxyl groups on the surface of alumina play an important role in both the oxidation of Mo and the relative content of Mo species in the sonication product. The surface area of the alumina-coated Mo oxide is about 11 times larger than that of the bare alumina. An explanation for this change is offered.
Bibliographical noteFunding Information:
A. Gedanken thanks the Ministry of Science and Technology of Israel for supporting this research through a grant for infrastructure. Dr. Ziyi Zhong thanks the Kort Scholarship Foundation for supporting his postdoctoral fellowship. Dr. Yuri Koltypin thanks the Ministry of Absorptions of Israel, The Center for Absorption in Science for its financial help. The authors thank Professor M. Deutsch, of the Department of Physics, Bar-Ilan University, for extending the XRD facility, and Dr. Shifra Ho-chberg for editorial assistance.