| One of the major challenges faced in Direct alcohol fuel cells (DAFCs) is slow anode kinetics for the intermediates in alcohol electro-oxidation may occupy the reaction active sites. The Pt-based catalysts brings high cost and easily to adsorb CO-species and becomes inactive in alcohols, while the popular Pt-based binary-alloy catalysts still maintain the platinum content at 20 wt% which still have high cost.As transition elements, both nickel and tin have low price and are easy to find, and have been researched for the second metal in Pt-based binary metal catalysts for several years. But platinum content in popular catalysts are still 20 wt% with high cost.TiO2 is very stable in acidic solution. Titania nanotubes have more large surface area and more strong absorption of other substances then titania particles, they can raise the efficiency of TiO2. But they have to operate with other supports to reach the perfect effects, because of their conductivity.The paper, by continuum microwave irradiation, is preparing the anode catalysts of DMFCs by having the titania nanotubes doped into low platinum content (5 wt%) binary alloy systems and investigating their properties and performances. The introduction of TiO2NTs into the Pt-Ni/C catalyst can provide more adsorbed hydroxide group during alcohol oxidation reaction to quick remove CO-species from the active sites, and it strengthened the CO-tolerance and improved the performance of Pt-based binary metals catalysts. As the Pt content is only 5wt%, it kept down the catalyst cost. The main contents of the paper were listed as follows:1. The optimal craftworks of the synthesizing electro-catalysts were that when the power of microwave irradiation was 700W, the microwave reaction time was about 20 seconds every period (3 periods in all, divided by 10 seconds interval as cooling time).2. As TiO2 nanotubes doped into the low platinum content Pt-Ni/C catalysts, the performances in methanol system and ethanol system are researched respectively. The result of single cell test shows that the highest power density of DMFC obtained by using the Pt-Ni-TiO2NT/C as anode material is 9.74 mW/cm2, which is about 60% of the corresponding results of commercial Pt-Ru catalysts (20wt% Pt-content) with equal catalyst-loading. XPS spectrums shows that the content of simple Pt and hydroxide group on catalyst surface is observed increased. In conclusion, the presence of TiO2 nanotubes modifies the electronic structure of Pt in terms of creating more metallic sites. More hydroxide groups are also generated, which participate in the oxidative removal of the reaction intermediates thus increasing catalyst efficacy Pt catalysts by minimizing site-blocking.3. As TiO2 nanotubes doped into the low platinum content Pt-Sn/C catalysts, Pt:Ni=3:1 and Pt:TiO2NT=1:7 are the optimized mole ratio of Pt, Ni and TiO2NT in the catalyst. XRD and XPS are used to learn the lattice patterns and the existence form, respectively. XPS spectrum shows that Sn mainly exists as SnO and the content of simple Pt and hydroxide group on catalyst surface are increased. The presence of TiO2 nanotubes modifies the electronic structure of Pt in terms of creating more metallic sites. More hydroxide groups can remove the CO-species during ethanol oxidation reaction. But it doesn't show good performance in methanol system.4. In conclusion from the commonness of the two binary catalyst systems, as TiO2NT introduced into low Pt content binary metal catalysts by continuous microwave irradiation, the platinum and the metal (as nickle and tin) are distributed on the surface of catalysts while TiO2 nanotubes being highly dispersed on the support as a promoter but neither an active component nor support. The presence of TiO2 nanotubes modifies the electronic structure of Pt in terms of creating more metallic sites. More hydroxide groups are also generated, which participate in the oxidative removal of the reaction intermediates thus increasing catalyst efficacy Pt catalysts by minimizing site-blocking. However, as different second metal being used, it would show different performances based on the difference of the binary metal systems in themselves. |
