Study On Carbon Nanotube-Based Electrodes In Direct Alcohol Fuel Cell

Direct alcohol fuel cell (DAFC) is a promising device due to the free-pollution, the abundant sources, high energy transfer efficiency, the safety for the storage and transportation of the fuel and there are potential application for portable equipment, electric car and field power, which is of great importance for sovling scarcity of energy sources and environmental pollution. However, the most problems are the low electrochemical activity of anodic catalysts and high "methanol crossover" through the proton exchange membrane (PEM) which will depress the activity of cathode. In addition, noble metal Pt with high price is still the primary catalysts for DAFC. Therefore, it is necessary to prepare catalysts with low loading and high activity, which is also an effective way to reduce the cost of fuel cell. In this paper, carbon nanotubes (CNTs) grown directly on graphite substrate were used as the support for noble metal catalysts, which will improve the efficiency of catalysts. In order to solve the most problems of DAFC, new DAFC electrodes were prepared in this paper and their electrochemcal properties were investigated in detail. The main results obtained in this paper are presented as follows: 1. Ethanol were used as the fuel of DAFC; Pt and Pt-Ru nanoparticles were deposited on surface of carbon nanotubes by potential-step method. The results indicate that the Pt/CNT/graphite and Pt-Ru/CNT/graphite electrodes have much higher electrocatalytic activities for ethanol oxidation than that of Pt/graphite electrode. The effects of temperature, scan rate and ethanol concentration were evaluated in detail. In addtion, the long-term cyclic stability of Pt-Ru/CNT/graphite electrode is superior to that of Pt/CNT/graphite electrode, Pt-Ru/CNT/graphite electrode is an excellent anode for direct ethanol fuel cells (DEFCs). 2. The spontaneous reduction of PtCl62-ion on surface of CNTs was achieved in aqueous solution for the first time and the electrocatalytic activities of SR-Pt catalysts for methanol oxidaiton were studied. Comparing with other Pt and PtRu catalysts prepared by H2 reduction or electrodeposition, SR-Pt catalysts show outstanding anti-poisoning ability and long-term cyclic stability. A possible mechanism for methanol oxidation on as-prepared Pt/CNT catalysts was also concluded. 3. Prussian blue (PB) was used to prevent the methanol molecule from contacting with Pt catalysts for the first time and PB/Pt/CNT/graphite electrode was prepared as direct methanol fuel cell (DMFC) cathode. The results show that in the presence of PB, methanol oxidation reaction is inhibited absolutely in 0.1 M H2SO4 + 0.1 M CH3OH aqueous solution, but the electrocatalytic activity of PB/Pt/CNT/graphite electrode for oxygen reduction reaction remains. In addition, PB/Pt/CNT/graphite electrode has excellent storage stability.