Modulating catalytic oxygen activation over Pt-TiO2/SiO2 catalysts by defect engineering of a TiO2/SiO2 support

Binary TiO2/SiO2 oxides were synthesized via flame spray pyrolysis as supports for a Pt catalyst. The effect of the mole ratio of the silica and on the catalyst characteristics and...

A Si-based suspended tunnel structure with trapezoidal section by two - step etching

Two - step etching method is used to prepare Si-based suspended tunnel structure with trapezoidal section. In the first wet etching, surfactant Triton-X-100 is added to TMAH enchant to inhibit crystal plane characteristics. Bulk Si Rib with trapezoidal cross section is formed, with inclination of side and height being modulated by changing etching time, so as to obtain good stability. After SiO2 support layer is grown by thermal oxidation, pure 25%TMAH is used in the second wet etching to quickly lateral etch and undercut the bulk silicon under the support layer and form a suspended structure along <100> opening. Using additive-no additive two-step etching method, suspended structure with high stability and compressive strength, good insulation characteristics, high yield can be prepared. It lays a solid foundation for the development of high sensitivity photo, thermal, chemical and gas sensors.

Highly Dispersed and Stable Ni/SBA-15 Catalyst for Reverse Water-Gas Shift Reaction

A 1%Ni/SBA-15(P) catalyst was synthesized with a P123-assisted impregnation method, which exhibited high CO2 conversion and stability in the reverse water-gas shift reaction. For the 1%Ni/SBA-15(P) catalyst, TEM and TPR characterizations demonstrated that the highly dispersed NiO particles at about 3 nm strongly interacted with the SiO2 support. During reverse water-gas shift reaction, the 1%Ni/SBA-15(P) catalyst exhibited higher CO2 conversion than the 1%Ni/SBA-15 catalyst prepared by the conventional impregnation method without P123. The CO2 conversion of the 1%Ni/SBA-15(P) catalyst at 700 °C was 33.7%, which was three times that of the 1%Ni/SBA-15 catalyst. Moreover, the former catalyst was stable at 700 °C within 1000 min. The good activity and stability of the 1%Ni/SBA-15(P) catalyst was owing to small Ni particles that strongly interacted with SBA-15.

Synthesis of Al – Fe/SiO2 and Al – Co/SiO2 catalysts by solid-phase method

Powders of catalysts from aluminides Fe and Co on a SiO2 support (33.3 wt. %) were obtained by mechano-thermal synthesis. The formation of large powder fractions (> 100 μm) was experimentally established. The fractions of these fractions for Fe – Al – SiO2 and Co – Al – SiO2 respectively amounted to ~ 43 % and ~ 55 %, which is a positive result for further catalytic studies. After annealing the powders at 700 and 900 °C in vacuum, the SiO2 support and compounds: Co27Al73 (close in composition to CoAl3, Co4Al13 type intermetallic compounds), Fe3Al intermetallic compound with iron silicide type Fe0.9Si0.1 and compound Al0,3Fe3Si0.7 in small volumes. On the synthesis of cobalt aluminides, a conclusion has been made about more efficient annealing at 900 °C than at 700 °C. For Fe – Al – SiO2 powders, it is advisable to anneal in the temperature range 700 – 750 °C with the assumption that the SiO2 support influences the thermosynthesis of iron aluminides. An experimental analysis of the morphology and elemental composition of the surface of the obtained samples is presented. It was found that the catalyst powders have medium sphericity and angularity. Fe – Al – SiO2 powders have a more developed surface than Co – Al – SiO2. Lower intermetallics are predominantly formed on the surface of the Co – Al – SiO2 sample. The correction of the mechanical alloying modes by means of the fragmentation of the process, changes in the intensity of its parameters, and various annealing conditions for Co – Al – SiO2 and Fe – Al – SiO2 are proposed.

Characterizations and nitrate adsorption capacity of Amine-SiO2 material

Amine-SiO2 material (basically on silicon dioxide) was synthesized by the grafting method with triamine silane to form activated amine groups on the surface of SiO2 support and was applied as a novel adsorbent for nitrate removal from aqueous solution. The characterizations of Amine-SiO2 were determined by using TGA, FTIR, BET, SEM. Nitrate adsorption capacity and durability of Amine-SiO2 were compared with the anion exchange resin (Akualite A420 commercial). The results showed that Amine-SiO2 had high nitrate adsorption capacity, ~ 1.14 fold higher than the Akualite A420 ion exchange resin, based on the adsorption efficiency. This might be due to a strong affinity for nitrate ions of the activated amine groups on the surface of SiO2 support. In addition, the experimental results also proved that Amine-SiO2 material had good durability (stable performance after 10 regeneration times).

Highly-Dispersed Ni-NiO Nanoparticles Anchored on an SiO2 Support for an Enhanced CO Methanation Performance

Highly-dispersed Ni-NiO nanoparticles was successfully anchored on an SiO2 support via a one-pot synthesis and used as heterogeneous catalysts for CO methanation. The as-obtained Ni-NiO/SiO2 catalyst possessed a high Ni content of 87.8 wt.% and exhibited a large specific surface area of 71 m2g−1 with a main pore diameter of 16.7 nm. Compared with an H2-reduced Ni-NiO/SiO2 (i.e., Ni/SiO2) catalyst, the Ni-NiO/SiO2 displayed a superior CO methanation performance. At the temperature of 350 °C, the Ni-NiO/SiO2 showed a CO conversion of 97.1% and CH4 selectivity of 81.9%, which are much better values than those of Ni/SiO2. After a 50-h stability test, the Ni-NiO/SiO2 catalyst still had an overwhelming stability retention of 97.2%, which was superior to the 72.8% value of the Ni/SiO2 catalyst.

Facile formation of CoN4 active sites onto a SiO2 support to achieve robust CO2 and proton reduction in a noble-metal-free photocatalytic system

The conversion of CO2 and protons to solar fuels (CO and H2) is achieved by CoN4 active sites anchored on SiO2.