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One step NaBH reduction of Pt-Ru-Ni catalysts on different types of carbon supports for direct ethanol fuel cells: Synthesis characterization 《燃料化学学报》2017,45(5):596-607
The ternary catalyst Pt75Ru5Ni20 was conducted on various types of carbon supports including functionalized Vulcan XC-72R (f-CB), functionalized multi-walled carbon nanotubes (f-MWCNT), and mesoporous carbon (PC-Zn-succinic) by sodium borohydride chemical reduction method to improve the ethanol electrooxidation reaction (EOR) for direct ethanol fuel cell (DEFC). It was found that the particle size of the metals on f-MWCNT was 5.20 nm with good particle dispersion. The alloy formation of ternary catalyst was confirmed by XRD and more clearly described by SEM element mapping, which was relevant to the efficiency of the catalysts. Moreover, the mechanism of ethanol electrooxidation reaction based on the surface reaction was more understanding. The activity and stability for ethanol electrooxidation reaction (EOR) were investigated using cyclic voltammetry and chronoamperometry, respectively. The highest activity and stability for EOR were observed from Pt75Ru5Ni20/f-MWCNT due to a good metal-carbon interaction. Ru and Ni presented in Pt-Ru-Ni alloy improved the activity and stability of ternary catalysts for EOR. Moreover, the reduction of Pt content in ternary catalyst led to the catalyst cost deduction in DEFC. 相似文献
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Thongthai Witoon Metta Chareonpanich Jumras Limtrakul 《Journal of Sol-Gel Science and Technology》2009,51(2):146-152
In this study, the formation of silica–chitosan hybrid materials via sol–gel process under pH values of 2–6 were investigated
using N2 sorption analysis, scanning electron microscopy, transmission electron microscopy, thermal analysis and zeta potential analyzer.
The hierarchical structure consisting of meso- and macropore was formed when pH value was higher than 2. Mesopores were formed
as the interparticle channels of silica nanoparticles aggregates, whereas macropores were the void between the aggregates
(clusters). The clusters size was decreased with increasing the pH value, resulting in the increase of the macroporosity.
The thermal conductivity of the products was controlled in the range of 0.06 and 0.13 W m−1 K−1 by varying the product porosity between 88 and 69% (pH 6 and pH 2, respectively). 相似文献
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Thongthai Witoon Soponwit Tepsarn Puscharapon Kittipokin Ben Embley Metta Chareonpanich 《Journal of Non》2011,357(19-20):3513-3519
Understanding the interaction between chitosan molecules and sodium silicate is one of the principal objectives for the development of new environmentally benign strategies for the synthesis of low-cost porous silica with hierarchical structure. In this work, we have explored two essential factors simultaneously: chitosan/silica ratios (0.1, 0.4, 0.8 and 1.6) and pH values of the mixture (3, 5 and 6). The obtained silica–chitosan composite and the calcined products were investigated by using thermal gravimetric analysis, N2-physisorption, scanning electron microscopy, and transmission electron microscopy. Rapid precipitation of silica–chitosan composite occurred because of the initial pH values of the chitosan and sodium silicate solutions. The amount of precipitating silica–chitosan composite was increased with increasing pH value of the mixture and chitosan/silica ratios but it did not change with the decrease of pH value of the mixture. The as-synthesized products prepared at pH 3 and 6 showed macroscopic two-solid phases (consisting of silica-rich phase and chitosan-rich phase), while those prepared at pH 5 displayed liquid and solid phases. At pH 3, a unimodal porous structure was found for the calcined products obtained from the silica-rich phase while a hierarchical structure was found for those obtained from the chitosan-rich phase; meanwhile, a hierarchical structure occurred for all calcined products prepared at pH 6. Different hierarchical structures of the silica products could be obtained by changing pH value of the mixture and chitosan/silica ratios. 相似文献
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Thongthai Witoon Metta Chareonpanich Jumras Limtrakul 《Journal of Sol-Gel Science and Technology》2010,56(3):270-277
The uses of low cost, renewable, environmentally friendly chitosan biopolymer as the structural template to control the size
of silica particles in the range of nanometer scales are attractive for their practical industrial applications. In this paper,
the nanostructured silica was synthesized using sodium silicate as the silica source and chitosan as the template under mild
conditions. Effects of chitosan/silica ratio and aging temperature on the formation and the control of nanostructured silica
was investigated by using thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), N2-sorption measurement, and transmission electron microscopy (TEM). It was found that the silica products were composed of
the aggregates of primary silica nanoparticles and nanostructured silica units. At low aging temperature, the size of nanostructured
silica was decreased when increasing the chitosan/silica ratio from 0.1 to 0.4. In contrast, the reverse trend was observed
at the chitosan/silica ratio of higher than 0.4. The increase of aging temperature led to the formation of larger primary
silica nanoparticles and nanostructured silica, and also promoted the formation of silica/chitosan composites. The fractal
dimension calculated using modified FHH method found the linear correlation at two different regimes which might reflect the
aggregates of silica products at different length scales. 相似文献
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