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The catalyst layer is a key component in the proton exchange membrane fuel cell (PEMFC) for it is where the conversion of fuel into electricity takes place. Traditionally, electrocatalyst is uniformly distributed in the catalyst layers of the membrane electrode assembly (MEA) and the high Pt consumption in catalyst layers blocks the widely use of PEMFC. Here we proposed a Pt content and pore structure gradient distributed, two-layer catalyst layer for PEMFC to improve the MEA performance. Energy-dispersive X-ray (EDX) spectroscopy results show Pt nanoparticles gradient distributed on the vertical direction of catalyst layer. The pore size in the Pt poor layer is larger than that in the Pt rich layer, and this structure can improve the Pt utilization and enhance the mass transfer in the catalyst layer. The single cell test result shows this new MEA has a better performance (11%) than the traditional MEA.

The multi-walled carbon nanotubes (MWNTs) were treated by different methods with mixed acid to introduce defects. Then the Pt/MWNTs catalyst was synthesized by polyol method. After that, a two layer buckypaper was prepared using a filtration method. The electrochemical characteristics were studied by cyclic voltammetry (CV) and liner sweep voltammetry (LSV) techniques. The results showed that the ultrasonic treatment is the best way to treat the MWNTs and increases the Pt loading in the catalyst compared with other treatments. The CV performance of the Pt/MWNTs-Ultrasonic catalyst is equivalent with the Pt/C JM catalyst and the LSV result of Pt/MWNTs-Ultrasonic catalyst is better than the Pt/C JM catalyst. The Pt/Buckypaper catalyst layer also showed good ORR performance. With the advantage of easy preparation, the Pt/Buckypaper catalyst layer has a potential to be widely used in PEMFCs.

As the key material of proton exchange membrane fuel cell (PEMFC), the carbon supported Pt nanoparticles are the most widely used catalyst for cathode and anode of PEMFC1. Unfortunately, the corrosion of the carbon support can lead to a decrease of catalyst performance, stability and lifetime. And then, the research on unsupported Pt catalyst is very important for the commercialization of PEMFC. We firstly prepared PtO2 colloidal solution and an unsupported Pt catalyst was obtained by the reduction of PtO2 colloidal solution. The microstructure and morphology of samples were characterized transmission electron microscopy(TEM). The electrocatalytic performances were measured by cyclic voltammetry(CV), linear sweep voltammetry(LSV) techniques. Reaction time, temperature and pH value have significant influence on catalyst performance. The results were compared with Pt/C-JM.TEM results show that average particle size of this catalyst is 2.46 nm. After treatment at 50 oC for 1h in H2 andN2 mixture (VN2:VH2=9:1), the ECA increased to 43.15 m2·g-1. It has high oxygen reduction reaction (ORR) onset reduction potential (0.98 V). Acknowledgments The authors acknowledge the support from the National Natural Science Foundation of China (21006073), the Scholarship Council and the Fundamental Research Funds for the Central Universities at Tongji University. Reference J.S. Zheng, X.Z. Wang, Fu R, D.J. Yang, P. Li, H. Lv, J.X. Ma. Int J Hydrogen Energy 37(2012) 4639. J.S. Zheng, X.Z. Wang, Fu R, D.J. Yang, P. Li, H. Lv, J.X. New Carbon Materials 4 (2011) 262. Figure 1