Study On Carbon Nanotube-Based Electrode In Direct Methanol Fuel Cell

The direct methanol fuel cell (DMFC) has been received widespread attention due to the abundant sources, the price, the safety of the storage and transportation of the fuel. However, the performances of DMFC are related to the dispersion and diameter of the electrocatalysts used and the structure of catalyst supports. Carbon nanotubes , have been received much attention in catalyst supports due to their extraordinary electrical conductivity and high surface area. In this paper, the anode electrocatalyst of DMFC was electrodeposited at the first time on the surface of carbon nanotubes, which are directly grown on the graphite substrate, and the electrochemical properties of these new type electrodes are investigated in methanol solutions. The main results obtained in this paper are shown as follows:1. The Pt, Pt-Ru electrocatalysts were electrodeposited by potentiostatic method on the surface of carbon nanotubes. The morphology of the Pt/CNT/C and Pt-Ru/CNT/C electrodes were investigated by TEM and SEM. The catalysts are in the high dispersion and the particle size is 60 - 80nm. The Pt/CNT/C , Pt-Ru/CNT/C , Nafion/Pt/CNT/C and Nafion/Pt-Ru/CNT/C are prepared successfully in this paper.2. The Pt/CNT/C electrode shows high electrocatalytic properties for methanol oxidation. For the same Pt deposition charge (Q = 3.72 10-3C/cm2), the electrocatalytical activity of Pt/CNT/C electrode is about 2.3 times as high as that of Pt/C electrode. After 500 cycles, the electrocatalytic activity of Pt/CNT/C electrode still remains the 71% value of maximum, but the long-term stability needs to be improved more in the future. The oxidation of methanol at Pt/CNT/C electrode is controlled by diffusion process.3. The effect of the ratios of Pt to Ru (Rpt/RU) in the deposition bath solution on the electrocatalytical properties of Pt-Ru/CNT/C electrode was investigated. The results show that the Pt-Ru/CNT/C electrode has good electrocatalytic properties for methanol oxidation at RPt/RU= 1. When the deposition charge is 1.17 10-3C/cm , the electrocatalytic properties and the long-term stability of Pt-Ru/CNT/C electrode are better than that of Pt/CNT/C electrode. The electrocatalytical activity of the Pt-Ru/CNT/C electrode remains 80% value of that at the first cycle after 600 cycles. The methanol oxidation reaction at Pt-Ru/CNT/C electrode is still controlled by diffusion process though it is complexity.4. The Nafion/Pt/CNT/C and Nafion/Pt-Ru/CNT/C electrodes were prepared in thispaper. The effect of the amount of Nafion to the electrocatalytic activity of the Pt/CNT/C and Pt-Ru/CNT/C electrodes were investigated. The results show that when catalyst deposition charge is 1.31 10-3C/cm2, the highest electrocatalytic activity of Nafion/Pt/CNT/C and Nafion/Pt-Ru/CNT/C electrodes can be observed at the addition of 4 l(1.08 g/cm2) and 2 l (0.54 g/cm2) Nafion solutions, respectively. On the other hand, electrochemical impedance study (EIS) shows that the impendence of the electrode increases with the addition of the Nafion. However, the long-term stabilities of Nafion/Pt/CNT/C and Nafion/Pt-Ru/CNT/C electrodes are better than that of Pt/CNT/C and Pt-Ru/CNT/C electrode, This is implies that Nafion/Pt/CNT/C and Nafion/Pt-Ru/CNT/C electrodes are good for practical application in DMFC.