Fe Ions-Doped TiO2 Aerogels as Catalysts of Oxygen Reduction Reactions in Alkaline Solutions.

Aerogels have interconnected networks and preeminent pore structures. When used as the catalysts for oxygen reduction reaction (ORR), they can facilitate the mass transfer and expose more active sites. Here, we synthesized the Fe-doped titanium oxide-based aerogels (TA/Fes) by the sol-gel method combined with thermal treatment. The specific surface areas of the TA/Fes ranged from 475 to 774 m2·g-1, and the pore volumes varied from 0.96 to 1.72 cm3·g-1. The doping effect of the Fe ions and the oxygen vacancies in anatase enhance the electrical conductivity, leading to the low Rct (313.3-828.2 Ω). All samples showed excellent stability (2.0-4.5 mV) and 4e- pathway. The limiting current density of TA/Fe3 reached 5.34 mA·cm-2, which was comparable to that of commercial Pt/C. The preparation method is inspiring and the as-prepared aerogel catalysts have potential in promoting the scale of fuel cells.

Thermal and Mechanical Performances of the Superflexible, Hydrophobic, Silica-Based Aerogel for Thermal Insulation at Ultralow Temperature.

A superflexible hydrophobic silica-based aerogel (FHSA) was prepared via a facile sol-gel process and ambient pressure drying method. The FHSA was treated at different temperatures varying from -196 to 450 °C to evaluate its thermal and mechanical performances. The evolutions of the physical property, hydrophobicity, microstructure, pore structure, and chemical structure of the FHSA with the various treatment temperatures were investigated comprehensively. The structure of the FHSA did not show an obvious change after treatment in the liquid nitrogen. The bulk density of the FHSA increased from 0.047 to 0.077 g cm-3 when the thermal treatment temperature increased from 25 to 450 °C. The specific surface area and pore volume of the FHSA increased with the treatment temperature owing to the decomposition of the organic moieties. The Fourier transform infrared spectra showed that the methyl groups in the FHSA had excellent thermostability up to 400 °C. The water contact angles of the FHSA after treatment at -196, 25, 200, 300, 350, 400, and 450 °C were 131, 151, 162, 150, 132, 119, and 34°, respectively. The thermal conductivity of the FHSA at a low temperature of -10 °C was 0.022 W m-1 K-1. The reversible deformation rate of the FHSA was more than 80% within 100 compression cycles. After treatment in liquid nitrogen, the reversible deformation rate of the FHSA remained at 50%. The synthesis method of the FHSA is simple, the resulting FHSA showed good performance both in thermostability and flexibility, and it is promisingly applied for thermal insulation and sealing in ultralow-temperature environments.