| As a sustained portable power supply, direct ethanol fuel cell (DEFC) plays a significant role in promoting the development of 3G era. It can resolve some problems of portable electronic devices, such as limited continuous working time and long charging time. At present, the DEFC research just starts, the key problem is how to improve catalyst activity and reduce cost. Researchers used to focus on the Pt modification. Binary and ternary Pt-based catalysts have been systematically studied. Ethanol electrooxidation on Pt is a structure-sensitive reaction. It is influenced by the catalyst surface geometry and electronic structure, such as the Pt-Pt bond energy, d-state electronic orbital. Ethanol electrooxidation on electrode surface is a three-phase reaction, affected by combined factors of the mass transfer, reaction active site, electron and proton transfer. In this paper, we focus on supporting materials, systematically study the interaction between support and metal in order to choose suitable catalyst support for the ethanol electrooxidation. The support-metal interaction may help to improve the activity and utility of Pt, reduce the cost.First, Pt embedded carbon xerogel catalysts are prepared by sol-gel method. By adjusting the pH value, we could vary carbon particle size and pore size distribution. A series of differ surface area (400 m2/g-600 m2/g) catalysts are prepared. Their pore size distribution varies from macro pore to micro pore. When the pH value is 7.05, as prepared Pt/CX-7.05 catalyst has the best catalytic activity for ethanol electrooxidation. Its Pt utilization reachs 39.7%, which is more than 4 times than that of the 20% Pt/C commercial catalyst. Its electrochemical surface area of Pt is 134.2m2/g, about 1.6 times than that of the 20% Pt/C commercial catalyst. The strong interaction between carbon xerogel and Pt of Pt/CX-7.05 catalyst makes its CO oxidation onset potential lower about 60mV than that of the 20% Pt/C commercial catalyst, enhances its CO-tolerance. The large surface area and mesoporous structure of Pt/CX-7.05 catalyst is good for the transmission of ethanol and intermediates, and efficiently improves the Pt utilization. The high graphitization of carbon xerogel increases the catalyst conductivity. In addition, this method directly embeds Pt in carbon during the carbon xerogel preparation, avoiding the traditional cumbersome process (make carbon, then modified, and Pt loading). The use of EDTA could effectively protect Pt from agglomerating.Secondly, WO3 modified VulcanXC-72 is used as composite support to prepare a series of Ptx/WO3-C catalysts, the atomic rate of Pt and W varies from 2.6:1,5.6:1 to 7.5:1. We find that WO3 not only has the―hydrogen spillover‖effect, but also has electronic modulation effect on Pt. The Pt lattice constants of the Ptx/WO3-C catalysts are enlarged, which is good for ethanol adsorption and dehydrogenation. It also weakens the Pt-CO bond, lowering the onset potential of the CO electrooxidation reaction. The Pt5.6/WO3-C catalyst shows the highest catalytic activity. Because the synergetic effect between WO3 and Pt occurs on their adjacent interface, it is affected by the distribution and size of the WO3 and Pt particles.We systematically study the performance of SWNT supported Pt-based catalysts in DEFC. SWNTs are pretreated by H2O2, HNO3 and the mixture acid (made of H2SO4 and HNO3), respectively. The effect of differ pretreatments is studied. After treated by HNO3, the winding original SWNT is straightened, its surface area decreases slightly from 292.0m2/g to 255.4m2/g, and its average pore size decreases to 7nm. As prepared Pt/SWNT-N catalyst has the best electrocatalytic activity for the ethanol oxidation reaction. The SWNT-O, treated by H2O2, has the largest surface area (401.4m2/g). Its average pore size is around 7nm. But the EAS of the Pt/SWNT-O catalyst is smaller than that of the Pt/SWNT-N catalyst. Because SWNT-O has more winding tubes, which means SWNT-O has more structure defects than SWNT-N. The Pt lattice constants of the SWNT supported Pt catalysts are smaller than that of the 20% Pt/C commercial catalyst, which is unfavorable for the hydrogen and ethanol absorption. However, the SWNT itself could adsorb hydrogen species, so to make up for the shortage.Additionally, SWNT-N, MWNT-N and VulcanXC-72 supported Pt catalysts are compared. We find the Pt/SWNT-N catalyst has the highest catalytic activity, and the Pt/MWNT-N catalyst has the lowest. Because MWNT-N has lots of structure defects and its surface area only is 49.7m2/g. Some Pt particles are deposited on the inner wall of the MWNT-N and blocked by the Pt particles loading on the tube mouth. The addition of Sn in Pt/SWNT-N is studied as well. There are both alloyed and oxidized Sn in PtSn/SWNT-N catalyst. The alloyed Sn enlarged the Pt lattice constant, which could improve the ethanol adsorption and weaken the Pt-CO bond. The Sn oxides adsorb–OHads at low potential, which would accelerate the oxidation of COads and improve the CO-tolerance. However, the SnOx are insulator. Too much addition of Sn would increase the resistance. Worse, SnOx has low corrosion resistance.Mo2C/C is used as oxygen reduction electrocatalyst for PEM fuel cell. The electrocatalytic activity for oxygen reduction is evaluated by single cell testing and cyclic voltammetry technique. Combined with the results gained by X-ray diffraction and X-ray photoelectron spectroscopy, respectively, its electrocatalytic mechanism is primarily analyzed. Mo2C/VC has electrocatalytic activity for oxygen reduction. The catalytic activity should be contributed to the redox of surface passivated species (MoOxCy and MoOz) and the oxygen migration in the crystal lattice of bulkβ- Mo2C.
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