Guoqing Zu

Silica-titania composite aerogel photocatalysts by chemical liquid deposition of titania onto nanoporous silica scaffolds.

Silica-titania composite aerogels were synthesized by chemical liquid deposition of titania onto nanoporous silica scaffolds. This novel deposition process was based on chemisorption of partially hydrolyzed titanium alkoxides from solution onto silica nanoparticle surfaces and subsequent hydrolysis and condensation to afford titania nanoparticles on the silica surface. The titania is homogeneously distributed in the silica-titania composite aerogels, and the titania content can be effectively controlled by regulating the deposition cycles. The resultant composite aerogel with 15 deposition cycles possessed a high specific surface area (SSA) of 425 m(2)/g, a small particle size of 5-14 nm, and a large pore volume and pore size of 2.41 cm(3)/g and 18.1 nm, respectively, after heat treatment at 600 °C and showed high photocatalytic activity in the photodegradation of methylene blue under UV-light irradiation. Its photocatalytic activity highly depends on the deposition cycles and heat treatment. The combination of small particle size, high SSA, and enhanced crystallinity after heat treatment at 600 °C contributes to the excellent photocatalytic property of the silica-titania composite aerogel. The higher SSAs compared to those of the reported titania aerogels (<200 m(2)/g at 600 °C) at high temperatures combined with the simple method makes the silica-titania aerogels promising candidates as photocatalysts.

Trimethylethoxysilane-modified super heat-resistant alumina aerogels for high-temperature thermal insulation and adsorption applications

The study of heat resistance of alumina aerogels has drawn great attention because of their high-temperature thermal insulation and catalyst applications. However, the main problem for the synthesis of heat-resistant alumina aerogels is their limited heat resistance and the drastic decrease of specific surface area upon heat treatment. Herein, trimethylethoxysilane (TMEO)-modified alumina aerogels are prepared by introduction of TMEO during sol–gel and supercritical fluid drying (SCFD) process. The introduced TMEO not only restricts the condensation of surface hydroxyl groups during aging and drying but also produces small silica particles on the alumina surface at high temperatures which inhibits the crystal growth upon heat treatment. Hence, the heat resistance of alumina aerogels is significantly enhanced after TMEO modification. The optimized TMEO-modified alumina aerogel has no cracks and little shrinkage during high-temperature SCFD, and shows no shrinkage and a high specific surface area of 147 m2 g−1 after heat treatment at 1200 °C. The TMEO-modified alumina aerogel possesses enhanced adsorption performance for gentian violet after firing at 1200 °C and shows low thermal conductivities of 0.13 and 0.18 W m−1 K−1 at 800 and 1000 °C, respectively. This may significantly contribute to their high-temperature applications such as thermal insulation, adsorption, catalysts, catalyst supports, etc.

Homogeneous deposition of Ni(OH) 2 onto cellulose-derived carbon aerogels for low-cost energy storage electrodes

Nano-architectured carbon aerogel/Ni(OH)2 composites have been prepared via a wet chemical approach that combines the sol–gel preparation of a highly porous carbon aerogel using microcrystalline cellulose, a low-cost and renewable polymer, as the carbon source and subsequent homogeneous deposition of Ni(OH)2 nanoparticles onto the backbone of the carbon aerogel via a two-step chemical precipitation process. The deposited Ni(OH)2 has small particle size (3–10 nm) and uniform dispersion and is well exposed to the electrolyte. The resulting composite possesses an interconnected, three-dimensional, high-surface-area (327 m2 g−1) nanostructure, which provides efficient transport of electrolyte ions and electrons and enables a fuller utilization of Ni(OH)2, thus leading to excellent electrochemical performance. The composite electrode exhibits high specific capacitance of 1906 and 1206 F g−1 at current density of 1 and 20 A g−1, respectively, which are much higher than those of Ni(OH)2. Moreover 89% capacitance is retained after 4000 cycles, implying a good cycling stability.

Highly thermally stable alumina-based aerogels modified by partially hydrolyzed aluminum tri-sec-butoxide

Highly thermally stable alumina-based aerogels are synthesized by the acetone–aniline in situ water formation method and modified by partially hydrolyzed aluminum tri-sec-butoxide at different temperatures (25, 45, and 60 °C). The effects of modification, especially modification temperature, on microstructure and thermal stability of alumina-based aerogels are investigated. After the modification, the morphologies of alumina-based aerogels change from the network structures with interconnected needle-like particles to those with stacked sheet-like particles, resulting in a better heat resistance. The thermal stability of alumina-based aerogels enhances with the increasing modification temperature, whereas the high temperature (more than 60 °C) would lead to the dissolution of wet gels during the modification process due to the high solubility. After annealing at 1200 °C for 2 h, the 45 °C-modified alumina-based aerogel exhibits the best thermal stability with the lowest linear shrinkage of ~7% and the highest specific surface area of 154 m2/g. In addition, the modified aerogels remain in the θ-Al2O3 phase while the unmodified one transforms into α-Al2O3 phase after 1300 °C annealing. The alumina-based aerogels are further reinforced by incorporating with mullite fiber felt and TiO2. The obtained composites show ultralow thermal conductivities of 0.065, 0.086, and 0.118 W/mK at 800, 1000, and 1200 °C, respectively.Graphical Abstract