| Proton exchange membrane fuel cell have attracted significant attention for its special property of high energy density, low operation temperature and environent-friendliness. Electrocatalyst is one of the key materials in fuel cells, which determines the performance, lifetime and cost of the fuel cells. Current Pt catalysts suffer from low durability which is hindering the implementation of fuel cells, metal-air batteries and electrochemical sensors. How to improve the catalyst durability has become a wide concen recently. Here, we use two different approaches to improve the durability. The first one is using a carbon nanotube film as a support material and controlling the morphology of the Pt catalyst. We report Pt catalysts with not only a high activity but also a high durability. This is achieved by electrodeposition of Pt crystal aggregates with a porous structure on a carbon nanotube film. Accelerated degradation testing shows that the new catalysts degrade very little even after 8000 potential cycles under harsh cycling conditions while the typical commercial catalyst of Pt/C loses its major portion of activity even in the first 1000 cycles. Based on the microstructure evolution and electrochemical evidence, the outstanding durability is attributed to the faceted nanocrystals and their interconnected porous network, both of which limit the pathways for Pt dissolution, migration, and agglomeration The second approach is a surface protecting technique. We cover a carbon nanotube film on the Pt/C catalyst layer to form a protecting layer. Accelerated degradation testing shows that the covered Pt/C performs with a much higher durability than that of the uncovered counterpart under otherwise identical conditions. This is attributed to the protection of the film that limits Pt dissolution, migration, and agglomeration. The new approaches reported here provide a new opportunity for developing next-generation electrocatalysts for promoting the real applications of fuel cells and many other devices. |
