| Direct formic acid fuel cell (DFAFC) is one kind of device which directly transform chemical energy, and attracting more and more interest from the world. However, there is a series of problems for this device, such as short service life, high cost and low efficiency, blocking them from the practical application.One of problems blocking DFAFC from the practical application is the slow kinetics of formic acid electro-oxidation due to CO poisoning to the Pt or PtRu anodic catalysts, resulting in a serious decline in the performance of DFAFC. Precious platinum(Pt) is mainly used for cathode catalysts, which is high cost. To improve the Pt utilization with minimizing the use of Pt is a priority. Also with the increase of run time , the precious cathode catalysts will reunion, and even the carrier has also been eroded. So the stability of the catalyst also need to be further strengthened. These problems were intensively studied in the chapter 3 and 4 of this thesis. The main results obtained are as follows:(1) First of all, TiO2 nanotube arrays (TiO2/Ti)are prepared in the titanium films by electrochemical anodic oxidation; secondly, Pd-TiO2/Ti catalysts are achieved by pulsed electrodeposition (ED) and magnetron sputter-replacement (SD); finally, we research that the Pd-TiO2/Ti catalyst electrodes how to make the formic acid oxidate in room temperature. To our delight, the following main conclusions are reached:①the onset potential of the oxidation for formic acid on the Pd-TiO2/Ti electrode is shifted to the negative direction relative to that on the electrode made from the commercial Pt/C catalysts (Johnson-Matthey Co. JM-Pt/C), and the both peak currents are nearly similar.②the catalytic activity and stability of SD-Pd-TiO2/Ti catalytic electrode for the oxidation of formic acid are better than that of SD-Pd/Ti catalytic electrode. Compared with the single Ti support, TiO2/Ti carrier can effectively make the Pd catalyst dispersed, in addition, the interaction between Pd and TiO2/Ti carrier (SMSI) favors adsorption and electronic transfer.③the stability of SD-Pd-TiO2/Ti is better than that of ED-Pd-TiO2/Ti for catalysing formic acid oxidation, resulting from the better dispersion and greater active surface.(2) Multi-walled carbon nanotubes with high porosity and large surface area are functioned to achieve carboxyl carbon nanotubes(COOH-CNTs). COOH-CNTs are used as support of Pt catalysts for catalysis of oxygen reduction reaction (ORR). We choose three different ways to prepare high dispersion and activity Pt/CNTs catalysts and reach the following main conclusions:①the addition of sodium citrate make citric acid ions and chloroplatinic acid ions to form coordination compound, which results in the platinum ions unconjugated in the reduction process, so that eventually the Pt/CNTs catalyst particles obtained are very small with a mean particle size of 2.5nm.②the most optimal way and the specific parameters of reduction are obtained by means of several explorations to the reductions. Ethylene glycol is acted as reducing agent in autoclave(160℃) and PH is 11.③Pt/CNTs catalysts obtained presents well dispersion and uniform particle size with autoclave ethylene glycol reduction. We calculate the electrochemical surface area of the catalyst through CV curves, which is about 50.3 m2/g and far greater than that of the commercial catalyst JM-Pt/C(41.6 m2/g). More, the result of the single fuel cell tests is better than that of JM-Pt/C catalysts.④The initial experiments show that thiolation of carbon nanotubes possess better adsorption of platinum ions and a good anchor role, inducing that the Pt/CNTs catalyst is not easily reunion. They can be well supports for more stable catalysts.
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