Aqueous Route Synthesis of Mesoporous ZrO2 by Agarose Templation


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Mesoporous zirconia with high surface area has been synthesized using self-assembling agarose gel as a template. Agarose gel was formed in the presence of aqueous zirconyl nitrate solutions followed by precipitation of zirconium (hydr)oxide in the gel framework. A porous zirconia structure is obtained by pyrolysis of agarose. Fourier transform infrared spectroscopy is employed to assess the agarose-zirconia precursor interaction. Changes in the CO absorption bands indicate zirconium association with the OH groups of the agarose. Solid state 13C NMR studies of the nanocomposite showed a shift in intensity from 70 to 75 ppm indicating conversion of ~7% of COH to COZr. Scanning electron microscopy reveals that both agarose/zirconia nanocomposite and zirconia have similar morphological features as that of pure agarose gel confirming agarose templation. Phase transformation of zirconia from amorphous to tetragonal between 300°C and 500°C, and gradually into monoclinic phase up to 900°C is observed using X-ray powder diffraction. Specific surface area and pore size distribution are determined using nitrogen adsorption, employing BET and Barrett–Joyner–Halenda methods, respectively. The specific surface area of porous zirconia after heat treatment at 500°C was determined to be 86 m2/g, which reduced with increasing temperature to 13 m2/g above 900°C. Transmission electron microscopy confirmed the hierarchical structure of porous zirconia.