Core-Shell Structured PtxMoy@TiO2 Nanoparticles Synthesized by Reverse Microemulsion for Methanol Electrooxidation of Fuel Cells

The high price of catalyst and poor durability still restrict the development of fuel cells. In this work, core-shell structured PtxMoy@TiO2 nanoparticles with low Pt content are prepared by a reverse microemulsion method. The morphologies, particle size, structure, and composition of PtxMoy@TiO2 nanoparticles are examined by several techniques such as X-ray Diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy, etc. The PtxMoy@TiO2 electrocatalysts show significantly higher catalytic activity and better durability for methanol oxidation than the commercial Pt/C (ETEK). Compared to Pt/C catalyst, the enhancement of the electrochemical performance of PtxMoy@TiO2 electrocatalysts can be attributed to the core-shell structure and the shift of the d-band center of Pt atoms, which can weaken the adsorption strength toward CO molecules, facilitate the removal of the CO groups and improve electrocatalytic activity. The development of PtxMoy@TiO2 electrocatalysts is promising to reduce the use of noble metal Pt and has a great potential for application in fuel cells.

DIAMETER OF SODIUM DI-(2-ETHYLHEXYL)PHOSPHATE AND SODIUM DODECYLSULFATE REVERSE MICROEMULSION DROPLETS: EXPERIMENTAL DATA AND CALCULATION METHODS

The article is concerned with study of diameters of reverse microemulsion droplets depending on the water content in sodium bis-(2-ethylhexyl)phosphate – decane – water and sodium dodecylsulfate – butanol-1 – decane – water systems. Hydrodinamic diameters of microemulsion droplets were determined by the method of dynamic light scattering. It increases from 5.9 to 9.7 nm with an increase in the molar ratio of water and sodium bis-(2-ethylhexyl)phosphate from 5.0 to 20.0 in the sodium bis-(2-ethylhexyl)phosphate – decane – water microemulsion. Diameter of microemulsion droplets in the sodium dodecylsulfate – butanol-1 – decane – water system increases from 2.4 to 8.6 nm with an increase in the molar ratio of water and dodecylsulfate from 7.5 to 30.0. It was shown that the dependence of the diameter (d) on the water content (W) is linear. The applicability of the experimental data on the area per surfactant molecule at the "water-oil" interface and literature data on the values of molar volumes of microemulsion components to calculate the diameter of microemulsion droplets was analyzed. It was shown that the equation of the form d = kW + b is suitable for describing the dependence of the diameter of microemulsion droplets on the water content in the sodium dodecyl sulfate-butanol – 1-decane-water system. Parameters k and b of this equation are calculated using the value of the area per surfactant molecule at the "water-oil" interface, which can be obtained from experimental data on interfacial tension. Values of the diameter of microemulsion droplets calculated using the proposed equation differ by no more than 1 nm from the values obtained by dynamic light scattering. Values of the droplet diameter of microemulsion in the DEHPA – decane – water system calculated using this equation are underestimated by 1.0-2.5 nm relative to the experimental values, while the slope of the lines obtained from the experimental data and during the calculation is almost the same.