Abstract
An original, halide-free non-hydrolytic sol-gel route to mesoporous anatase TiO2 with hierarchical porosity and high specific surface area is reported. This route is based on the reaction at 200 °C of titanium (IV) isopropoxide with acetic anhydride, in the absence of a catalyst or of a solvent. NMR studies indicated that this method provides an efficient, truly non-hydrolytic and aprotic route to TiO2. Formation of the oxide involves acetoxylation and condensation successive reactions, both with ester elimination. The resulting TiO2 materials were nanocrystalline, even before calcination. Small (10 nm) anatase nanocrystals spontaneously aggregated to form mesoporous micron sized particles with high specific surface area (260 m 2 g-1 before calcination). Evaluation of the lithium storage performances showed a high reversible specific capacity, particularly for the non-calcined sample with the highest specific surface area favoring pseudo-capacitive storage: 253 mAh g-1 at 0.1C and 218 mAh g-1 at 1C (C = 336 mA g-1). This sample also showed good cyclability (>92% retention after 200 cycles at 336 mA g-1) with a high coulombic efficiency (99.8 %). Synthesis in the presence of a solvent (toluene or squalane) offers the possibility to tune the morphology and texture of the TiO2 nanomaterials.