(394e) Microwave-Assisted Synthesis and Characterization of Mesoporous Gallium Oxide

Gallium oxide-based catalysts are known to be active for oxidative dehydrogenation of light hydrocarbons, aromatization of light alkanes and selective catalytic reduction of NO_x by hydrocarbons in the presence of oxygen. Also, gallium oxide is a wide-band-gap semiconductor (Eg = 4.9 eV) that can be used not only as an oxygen gas sensor, but also as photocatalyst for water-splitting, nonoxidative coupling of methane and for the mineralization of gaseous benzene and its derivatives.

Gallium oxide has been synthesized by various conventional techniques such as thermal decomposition, homogeneous precipitation and surface layer adsorption. However these methods are time consuming and require relatively high reaction temperatures. Herein, we report the synthesis of mesoporous gallium oxide phases with uniform size via microwave-assisted heating of inorganic precursors and structure directing agents. Microwave heating offer several advantages over conventional heating approaches such as fast crystallization, phase selectivity, narrow particle size distribution, morphology and size control and rapid and uniform heating. Microwave-assisted approach led to the formation of nanocrystalline mesoporous gallium oxide phases at low reaction temperature (130˚C) and short reaction times (~15-120 min). The mesostructured gallium oxide displayed cubic spinel type structure with unimodal pore size distribution in the 6-12 nm range and surface areas as high as 200 m²/g. The resultant mesophases were characterized by BET N₂ adsorption-desorption isotherms, XRD, SAXS, SEM, and TEM. These mesophases are attractive for catalytic applications due to its high surface areas, tunability of pore sizes and crystallinity.

Keywords: Microwave-assisted synthesis, Mesoporous gallium oxide, Nanocrystals.