科研之友
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摘要
In this work, the effect of changing the stirring method and temperature on the physicochemical properties of metallic nanoparticles and core-shell nanostructures is shown. Magnetic (MS), mechanical (UT) and ultrasonic (USS) stirring are the methods of synthesis. The effect that, temperatures between 0 and 50 C, has on the structure and particle size of Fe304 nanoparticles is evaluated The results indicate that Fe304 prepared by the three methods presents a spinel-type crystalline structure. An increase in the synthesis temperature leads to highly crystalline powders. Afterwards, Pt is deposited by the UT method on Fe304 to form Fe304@Pt core-shell nanostructures. It is important to mention that the time used for the synthesis of the nanoparticles and the core-shell nanostructures is only one minute. The presence of Fe304 and Pt is confirmed by XRD and XPS. The metallic Pt phase is confirmed because the binding energy of Pt. 4f7/2 is associated to platinum in the zero-valent state. We evaluated the electrochemical activity of the Fe304@Pt core-shell nanostructures for the oxygen reduction reaction (ORR).. The novel materials show a high electrocatalytic activity and the Koutecicy-Levich analysis indicates that the reaction follows a 4 electron transfer mechanism on the Fe304@Pt nanostructures prepared by the three stirring processes. Moreover, the mass specific activity of the core-shell materials is as high as that obtained from the Pt-alone catalysts, suggesting that the amount of Pt in these electrodes can be reduced without decreasing the performance.
- 出版日期2012-7
