Ethers as Oxygen Donor and Carbon Source in Non‐hydrolytic Sol–Gel: One‐Pot, Atom‐Economic Synthesis of Mesoporous TiO₂–Carbon Nanocomposites

Abstract

Mesoporous TiO -carbon nanocomposites were synthesized using an original non-hydrolytic sol-gel (NHSG) route, based on the reaction of simple ethers (diisopropyl ether or tetrahydrofuran) with titanium tetrachloride. In this atom-economic, solvent-free process, the ether acts not only as an oxygen donor but also as the sole carbon source. Increasing the reaction temperature to 180 °C leads to the decomposition of the alkyl chloride by-product and to the formation of hydrocarbon polymers, which are converted to carbon by pyrolysis under argon. The carbon-TiO nanocomposites and their TiO counterparts (obtained by calcination) were characterized by nitrogen physisorption, XRD, solid state C NMR and Raman spectroscopies, SEM, and TEM. The nanocomposites are mesoporous with surface areas of up to 75 m g and pore sizes around 10 nm. They are composed of aggregated anatase nanocrystals coated by an amorphous carbon film. Playing on the nature of the ether and on the reaction temperature allows control over the carbon content in the nanocomposites. The nature of the ether also influences the size of the TiO crystallites and the morphology of the nanocomposite. To further characterize the carbon coating, the behavior of the carbon-TiO nanocomposites and bare TiO samples toward lithium insertion-deinsertion was investigated in half-cells. This simple NHSG approach should provide a general method for the synthesis of a wide range of carbon-metal oxide nanocomposites.

TinO2n−1 Suboxide Phases in TiO2/C Nanocomposites Engineered by Non-hydrolytic Sol–Gel with Enhanced Electrocatalytic Properties

“…The NHSG ether route has been extensively used to prepare metal oxides, especially for the synthesis of titanium oxides [ 33 , 35 , 45 ]. In our previous works, we reported on the synthesis of TiO 2 nanocrystals and TiO 2 /C nanocomposites from TiCl 4 and THF [ 42 ]. This approach is based on the intermediate formation of alkoxide groups, which then condense with Ti-Cl to form oxo bridges (step (1) in Figure 1 ).…”

“…The synthesis route is well-established and was already reported in our previous work [ 42 ]. Typically, TiCl 4 (12.52 mmol, 1.37 mL) and THF (25.04 mmol, 2.03 mL) were added into a 23 mL stainless steel digestion vessel with a polytetrafluoroethylene (PTFE) lining from Parr Instrument Company (Moline, IL, USA).…”

“…Nevertheless, NHSG has been established as a versatile methodology for the synthesis of mesoporous metal-oxides and mixed oxides in the absence of templating agents or costly drying procedures [ 35 ], metal oxide nanocrystals [ 36 , 37 , 38 , 39 ] as well as organic-inorganic hybrids [ 40 , 41 ] and metal-oxide/carbon nanocomposites [ 42 , 43 ]. Recently, we reported a solvent-free NHSG route to synthesize TiO 2 /C nanocomposites based on the reaction of simple ethers (diisopropyl ether or tetrahydrofuran, THF) in a stoichiometric amount with titanium tetrachloride [ 42 ]. In this atom-economic process, the ether acted not only as an oxygen donor, but also as the sole carbon source, yielding anatase TiO 2 nanocrystals coated by an amorphous carbon film [ 42 ].…”

“…Recently, we reported a solvent-free NHSG route to synthesize TiO 2 /C nanocomposites based on the reaction of simple ethers (diisopropyl ether or tetrahydrofuran, THF) in a stoichiometric amount with titanium tetrachloride [ 42 ]. In this atom-economic process, the ether acted not only as an oxygen donor, but also as the sole carbon source, yielding anatase TiO 2 nanocrystals coated by an amorphous carbon film [ 42 ]. Herein, we further extend this original approach to the preparation of titanium suboxides, by demonstrating that Ti n O 2 n −1 phases can be easily generated by partial carbothermal reduction of the TiO 2 /C nanocomposites at relatively low temperature, i.e., 950 °C, under argon flow.…”

Dehydration of Alginic Acid Cryogel by TiCl4 vapor: Direct Access to Mesoporous TiO2@C Nanocomposites and Their Performance in Lithium‐Ion Batteries

“…[43,44] However,t he practical application of these materialsi ss ignificantly hampered by their poor electronic conductivity and slow lithium-ion kinetics, which further limit their rate capability,a si nt he case of anatase TiO 2 . [45] To improvethe electronic conductivity,c arbon coating [46,47] or heteroatomd oping have been proposed. [48,49] Concerningl ithiumion kinetics,n anostructuring of TiO 2 with controlled porosity could be an effective solution as it can provide alarger contact area between the electrode and electrolyte, resulting in an enhancement of lithium-ion diffusioninside the electrode.…”