The Application Of Titanium Dioxide And Its Surface Modified Materials In Direct Fomic Acid Fuel Cells

The fuel cell is a device capable of generating chemical energy of fuel directly into electrical energy. It has many advantages such as high energy efficiency, high energy density, wide range of power and environmental friendliness. Its fuels are usually H₂, NH₃, CH₃OH, CH₃COOH, etc. Direct formic acid fuel cell ?DFAFC? has higher volume energy and safety during the process of using. At the same time, formic acid is easy to transport and store as a liquid fuel.DFAFC has broad application prospects in the field of portable power. Pt-based catalyst and Pd-based catalysts often used as anode catalysts of DFAFC. In comparison, the latter has more excellent catalytic properties for oxidation of formic acid. However, the performance of Pd-based catalysts needs to be further improved to achieve DFAFC commercialization.It is well known that catalyst supports have significant impact for improving catalyst activity and stability. TiO₂ became a hot area of photocatalyst research because of its non-toxic, cheap and good chemical stability and thermal stability, and high photocatalytic activity,etc. In recent years, the application of TiO₂ has begun to appear as a catalyst component of fuel cells. In this paper, the impact of the application of titanium dioxide and its Surface modified materials as anode catalyst support on the catalyst activity and stability has been researched. The main contents are as follows:?1?Pd/TiO₂-C composite catalyst was prepared with anatase titanium dioxide as catalyst support.its performance for formic acid electrocatalytic oxidation and the best ratio of TiO₂ and XC-72 carbon blacks were discussed. Studies have shown that the size of Pd nanoparticles supported on TiO₂ reduced, the synergistic effect between TiO₂ and Pd improved the activity of the catalyst, the synergistic effect and corrosion resistance of TiO₂ itself improved the stability of catalyst.When the mass ratio of TiO₂:C is 1:1, the catalyst performance is best.?2?Pd/TiO₂?P?-C catalyst was prepared Using TiO₂ modified by cationic polymer ?PDDA? as catalyst support. We studied the surface modification effect on the catalyst morphology and activity. The results showed that Pd nanoparticles supported on TiO₂ surface modified with PDDA have more uniform distribution and the reduced agglomeration. The mass activity and specific surface area activity all increased compared with the unmodified catalyst, which may be due to the metal surface adsorption for oxygen-containing groups decreased and more active sites be released. Continuous cyclic voltammograms and chronoam-perometry tests show that the stability of Pd/TiO₂?P?-C is much better than that of Pd/TiO₂-C.?3? PdCu/TiO₂?P?-C catalysts with different Pd and Cu mass ratio were prepared by electrostatic self-assembly on the surface of TiO₂ modified with cationic polymer PDDA. By XRD patterns, TEM and HRTEM pattern, PdCu alloy structure was confirmed, and Pd nanoparticles supported on the surface of TiO₂ modified with PDDA were more evenly distributed. Observed by TEM, when the Cu content is high, nanoparticles have a tendency to shift nanowires. The electrochemical test results show that the catalytic activity and stability of all three kinds of PdCu/TiO₂?P?-C catalyst are better than Pd/TiO₂?P?-C. The best in the three catalysts was PdCu/TiO₂ ?P?-C?1:2?, This is due to when the mass ratio of Pd and Cu was 1:2, the electronic effect between Pd and Cu was more significant, and the nanoparticles have not yet started to form linear structure.