| Summary: | 博士 === 國立交通大學 === 應用化學系碩博士班 === 103 === In this study, microspheres (MS), nanosheet spheres (NS), solid spheres with nanosheets (S-NS), channel-like (CT) and spongy-like porous TiO2 (PT) were synthesized with the assistance of the bio-ingredients as templates. We have proposed reaction pathways and the battery performance were also investigated.
First, facile route was established to synthesize high specific surface area TiO2 microspheres using basic amino acid (arginine or monosodium glutamate) as the templates. Titanium tetrabutoxide Ti(OBu)4 was used as the TiO2 precursor and absolute ethanol as the solvent. The solvothermal synthesis was carried out in a heated Teflon stainless-steel autoclave. The as-formed TiO2 precursor solid was further processed at 400 °C under air to generate the TiO2 microspheres (MS), nanosheet spheres (NS) and solid spheres with nanosheets (S-NS). They were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption-desorption analysis. The nitrogen adsorption-desorption isotherms revealed specific surface areas ranging from 30 to 122 m2/g. The products were used as an anode material for Li ion battery. The cells showed remarkable performance that the capacity of the the anode reached 167 mAh/g and 132 mAh/g under high charge/discharge rates, 5 C and 10 C respectively. They also demonstrated good cycling stability at varied charge/discharge rates.
Second, we employed a simple sol−gel process to fabricate TiO2 precursors by reacting titanium tetraisopropoxide (TTIP, Ti(OiPr)4), instant yeast, and glucose/starch molecules in an aqueous solution. Remarkably, the yeast cells maintained their physiological activities and occurred respirations in the aerobic reaction. Their respirations produced CO2 and H2O as the metabolites. The evolution of CO2 produces numerous channels in the inorganic matrix. After further processing, porous channel-like TiO2 (CT) was prepared. (macropore size: 1 – 3 µm) The BET/BJH results revealed specific surface areas ranging from 34 to 125 m2/g, and mesoporous size distributions (4 – 100 nm). In addition, potential applications of the as-prepared TiO2 in Li ion batteries were explored.
Finally, spongy-like porous TiO2 (PT) was synthesized by using yeast and glucose as the pore forming templates. TiCl4 in C2H5OH(l) containing NH4OH(aq.) was polymerized in the presence of instant yeast and glucose. The organic–inorganic hybrid precursor was further processed to generate macroporous anatase TiO2 (pore size: 2 – 3 µm) with mesopores (4 – 70 nm). The porous TiO2 was coated with a thin layer of carbon by chemical vapour deposition to generate the hierarchical C/TiO2 composite material. The porous products were investigated as anode materials for Li-ion batteries. The capacities of the hierarchical C/TiO2 electrode material remained 180 mAh/g and 142 mAh/g under high charge/discharge rates of 5 C and 10 C, respectively. It demonstrated good cycling stability of 318 mAh/g at 0.1 C at various discharge–charge rates. The excellent performance is attributed to the high specific surface areas and open spaces of the C/TiO2 allowing effortless intercalation/de-intercalation of Li ions.
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