Co@Pt/C core-shell catalysts have been synthesized by a two-step chemical reduction method, followed by heat treatment in a H2 and N2 mixture. High resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS) techniques were used to characterize the catalyst microstructure and morphology. The results indicate that the core-shell structure of Co rich in core and Pt rich in shell is formed and the nano-particles are highly dispersed on the surface of the carbon support. Heat treatment affects the structure and morphology of the catalysts. The electrocatalytic performance, kinetic characteristics of O2 reduction reaction (ORR), and durability of the catalysts were measured by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) techniques. It was found that the formation of the core-shell structure is favorable for improving the performance and utilization of Pt. The Co@Pt/C catalyst mechanism proceeds by an approximately four-electron pathway in acid solution, through which molecular oxygen is directly reduced to water. Compared with alloy catalysts, the formation of the core-shell structure obviously improves the catalyst durability.
Pt/cobalt-polypyrrole-carbon (Co-PPy-C)-supported catalysts were successfully prepared by pulse-microwave assisted chemical reduction. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) techniques were used to characterize the catalyst microstructure and morphology. The electrocatalytic performance, kinetic characteristics of the oxygen reduction reaction (ORR), and durability of the catalysts were measured by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) techniques. It was found that the particle size of Pt/Co-PPy-C was about 1.8 nm, which was smaller than that of commercial Pt/C (JM) catalysts (2.5 nm). The metal particles were well-dispersed on the carbon support. The electrochemical specific area (ECSA) of Pt/Co-PPy-C (75.1 m 2 • g -1 ) was much higher than that of Pt/C (JM) (51.3 m 2 •g -1 ). The results of XPS showed that most of the Pt in the catalysts was in the Pt(0) state, and XRD results showed that the form of Pt was mainly the facecentered cubic lattice. The Pt/Co-PPy-C catalyst had the same half-wave potential as Pt/C (JM) and showed higher ORR activity. The Pt/Co-PPy-C catalyst proceeded by an approximately four-electron pathway in acid solution. After 1000 cycles of CV, the ECSA attenuation rates of Pt/Co-PPy-C and Pt/C were 13.0% and 24.0%
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