LOS MONAGUILLOS [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201

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

A new strategy for the synthesis of mesoporous TiO2@C nanocomposites through the direct mineralization of seaweed-derived alginic acid cryogel by TiCl4 through a solid/vapor reaction pathway is presented. In this synthesis, alginic acid cryogel can have multiple roles; i) mesoporous template, ii) carbon source, and iii) oxygen source for the TiO2 precursor, TiCl4. The resulting TiO2@alginic acid composite was transformed either into pure mesoporous TiO2 by calcination or into mesoporous TiO2@C nanocomposites by pyrolysis. By comparing with a nonporous TiO2@C composite, the importance of the mesopores on the performance of electrodes for lithium-ion batteries based on mesoporous TiO2@C composite was clearly evidenced. In addition, the carbon matrix in the mesoporous TiO2@C nanocomposite also showed electrochemical activity versus lithium ions, providing twice the capacity of pure mesoporous TiO2 or alginic acid-derived mesoporous carbon (A600). Given the simplicity and environmental friendliness of the process, the mesoporous TiO2@C nanocomposite could satisfy the main prerequisites of green and sustainable chemistry while showing improved electrochemical performance as a negative electrode for lithium-ion batteries

Alginic acid-derived mesoporous carbonaceous materials (Starbon®) as negative electrodes for lithium ion batteries : Importance of porosity and electronic conductivity

Alginic acid-derived mesoporous carbonaceous materials (Starbon® A800 series) were investigated as negative electrodes for lithium ion batteries. To this extent, a set of mesoporous carbons with different pore volume and electronic conductivity was tested. The best electrochemical performance was obtained for A800 with High Pore Volume (A800HPV), which displays both the highest pore volume (0.9 cm3 g−1) and the highest electronic conductivity (84 S m−1) of the tested materials. When compared to a commercial mesoporous carbon, A800HPV was found to exhibit both better long-term stability, and a markedly improved rate capability. The presence of a hierarchical interconnected pore network in A800HPV, accounting for a high electrolyte accessibility, could lay at the origin of the good electrochemical performance. Overall, the electronic conductivity and the mesopore size appear to be the most important parameters, much more than the specific surface area. Finally, A800HPV electrodes display similar electrochemical performance when formulated with or without added conductive additive, which could make for a simpler and more eco-friendly electrode processing

Sustainable polysaccharide-derived mesoporous carbons (Starbon®) as additives in lithium-ion batteries negative electrodes

For the first time, polysaccharide-derived mesoporous carbonaceous materials (Starbon®) are used as carbon additives in Li-ion battery negative electrodes. A set of samples with pore volumes ranging from ≈0 to 0.91 cm3 g-1 was prepared to evidence the role of porosity in such sustainable carbon additives. Both pore volume and pore diameter have been found crucial parameters for improving the electrodes performance e.g. reversible capacity. Mesoporous carbons with large pore volumes and pore diameters provide efficient pathways for both lithium ions and electrons as proven by the improved electrochemical performances of Li4Ti5O12 (LTO) and TiO2 based electrodes compared to conventional carbon additives. The mesopores provide easy access for the electrolyte to the active material surface, and the fibrous morphology favors the connection of active materials particles. These results suggest that polysaccharide-derived mesoporous carbonaceous materials are promising, sustainable carbon additives for Li-ion batteries

Nonhydrolytic Sol-Gel Technology.

International audienc

Non-Hydrolytic Sol–Gel Routes

International audienc

Non-hydrolytic sol-gel routes to heterogeneous catalysts

Oxides and mixed oxides have a tremendous importance in the field of heterogeneous catalysis, serving either as catalysts or as supports for active species. The performance of a catalyst depends directly on its composition, texture, structure and surface properties, which have to be precisely controlled and adapted to each application. In this context, the sol-gel process is a unique tool for the preparation and understanding of catalytic materials, owing to its exceptional versatility. In the last 10 years, the non-hydrolytic sol-gel (NHSG) or non-aqueous sol-gel process based on nonhydrolytic condensations in nonaqueous media has established itself as a simple and powerful method for the design of a wide range of oxide, mixed oxide and hybrid materials with controlled composition, morphology, texture and structure. NHSG proved particularly interesting for the preparation of catalytic materials, notably mesoporous xerogels, single site catalysts and highly crystalline nanoparticles. This critical review addresses the application of NHSG to the preparation of heterogeneous catalysts, emphasizing the specificities of this process, and giving a comprehensive overview of the literature (251 references)

Water-Stable, Nonsiliceous Hybrid Materials with Tunable Porosity and Functionality: Bridged Titania-Bisphosphonates

International audienceCombining the properties of organic and inorganic moieties with high surface areas and pore volumes offers endless possibilities to design materials adapted to a wide range of advanced applications. The vast majority of mesoporous hybrid materials are siliceous materials, and developing low-cost synthetic methodologies leading to water stable nonsiliceous hybrid materials with controlled texture and functionality is essential. We report here an original strategy for the synthesis of mesoporous bridged titaniabisphosphonate hybrids based on a one-step, templateless nonhydrolytic sol−gel route. The reaction of Ti(O i Pr) 4 and a rigid bisphosphonate ester in the presence of Ac 2 O leads to the formation of TiO 2 anatase nanorods cross-linked by fully condensed bisphosphonate groups. The porosity can be readily adjusted over a wide range by changing the reaction conditions, and very high specific surface areas (up to 720 m 2 g −1) and pore volumes (up to 1.85 cm 3 g −1) can be reached. The texture is stable in aqueous media between pH 1 and pH 12. Furthermore, accessible functional organic groups can be easily incorporated using either functional bisphosphonates or easily available monophosphonate compounds. The accessibility of bipyridyl organic groups was checked by Cu 2+ adsorption from aqueous solutions. The unique combination of texture, functionality, and stability displayed by bridged titania-bisphosphonates makes these promising materials complementary of other hybrid materials such as organosilicas, MOFs, or mesoporous metal phosphonates

Mesoporous mixed oxide catalysts via non-hydrolytic sol–gel: A review

Despite the enormous amount of research dedicated to this topic in the last 20 years or so, there is still a need for a general, cost-effective methodology allowing the synthesis of mesoporous mixed oxide catalysts. This review deals with the synthesis and catalytic applications of mixed oxides prepared by the nonhydrolytic sol–gel (NHSG) process based on the reaction of chloride precursors with ether or alkoxide oxygen donors. This NHSG process offers simple, one-step syntheses of mixed oxides with well-controlled compositions and non-ordered mesoporous textures, avoiding the use of supercritical drying or templates. Over the last decade, this process has been used to prepare various mesoporous mixed oxide catalysts, which showed real potential in major reactions such as partial and total oxidation, reduction of NOx, alkene metathesis, or alkylation. The main reactions involved in this NHSG process and the characteristics of the resulting mixed oxides are described in the first part of this review, underlining the decisive advantages in terms of simplicity and of control (in terms of composition, homogeneity or texture) offered by this process. In a second part, the literature dealing with mixed oxide catalysts prepared by this NHSG method is exhaustively reviewed and the catalytic performance of NHSG catalysts is compared, whenever possible, to that of catalysts with similar compositions prepared by other methods. The excellent catalytic performances of NHSG-catalysts (notably Si Ti, Ti V and Si Al Mo catalysts) compared to state-of-the art aerogels or ordered mesoporous materials evidences the potential of this sol–gel method, which should open the door to the synthesis of improved catalysts and to the discovery of new catalysts

One-step nonhydrolytic sol–gel synthesis of mesoporous TiO2 phosphonate hybrid materials

Mesoporous TiO2–octylphosphonate hybrid materials were prepared in one step by a nonhydrolytic sol–gel method involving the reaction of Ti(OiPr)4, acetophenone (2 equiv) and diethyl octylphosphonate (from 0 to 0.2 equiv) at 200 °C for 12 hours, in toluene. The different samples were characterized by 31P magic angle spinning nuclear magnetic resonance, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and nitrogen physisorption. For P/Ti ratios up to 0.1, the hybrid materials can be described as aggregated, roughly spherical, crystalline anatase nanoparticles grafted by octylphosphonate groups via Ti–O–P bonds. The crystallite size decreases with the P/Ti ratio, leading to an increase of the specific surface area and a decrease of the pore size of the hybrid samples. For a P/Ti ratio of 0.2, the volume fraction of organic octyl groups exceeds 50%. The hybrid material becomes nonporous and can be described as amorphous TiO2 clusters modified by octylphosphonate units, where the octyl chains form an organic continuous matrix