Effect of heat treatment on the surface structure of Pd@Pt-Ni core-shell catalysts for the oxygen reduction reaction

To promote the commercialization of fuel cells by reducing cost, it is essential to reduce the amount of Pt in the catalyst and apply the low-Pt catalysts to the membrane electrode assembly (MEA). In this work, the high-performance Pd@Pt-Ni/C catalysts are prepared by a simple and effective method and applied in MEAs successfully. The particle size of the core-shell structure catalyst (Pd@Pt-Ni/C-200 degrees C) is around 4.5 nm and the particles are evenly dispersed on the carbon support. By optimizing the heat treatment temperature, it is found that the reduction of Pt on the surface of the catalyst can be achieved and the uniform distribution of the Pt-Ni shell can also be promoted to enhance the catalyst activity at 200 degrees C. Besides, the heat treatment at 200 degrees C can not only extend the stability of the catalyst but also avoid excessive particle size growth. The mass activity (MA) is nearly 5.1 times higher than that of commercial Pt/C catalysts (JM). After the accelerated degradation testing (ADT), the half-wave potential of Pd@Pt-Ni/C-200 degrees C only shifted 6 mV and MA could maintain 85.5%. In single-cell tests, the MEA prepared by Pd@Pt-Ni/C-200 degrees C has a maximum power density of 0.92 W/cm(2), which is 2.2% higher than that of Pt/C. Besides, the oxygen mass transfer resistance of MEA-Pd@Pt-Ni/C (23.0 s/m) is lower than that of MEA-Pt/C (26.2 s/m), indicating that the catalyst layer prepared by Pd@Pt-Ni/C is more conducive to oxygen transmission. It indicates that the Pd@ Pt-Ni/C core-shell catalyst can be the promising catalyst to be applied to proton exchange membrane fuel cells (PEMFC). (C) 2021 Published by Elsevier B.V.

Automated summary

In this study, high-performance Pd@Pt-Ni/C catalysts were successfully prepared and applied in MEAs, showing excellent catalytic performance and stability with a high mass activity. The research also indicates that the catalyst layer prepared by the Pd@Pt-Ni/C core-shell catalyst is more conducive to oxygen transmission, making it a promising candidate for proton exchange membrane fuel cells.