Preparation And Properties Research Of Low Platinum-Non-Metallic Composite Catalysts For Fuel Cells

Proton exchange membrane fuel cells(PEMFCs) are potential environmentally friendly power sources for portable electronic devices because they have high energy densities, simple system designs and low pollutant emissions. However, the widespread of commercialization and deployment of FCs into advanced sustainable energy infrastructures including the automotive sector is still limited by high cost and poor durability.In this work, we have designed a novel strategy to address both durability and activity issues via coating of nitrogen-doped graphitic carbon(NC) layer onto the surface of the Pt/C catalysts. The polydopamine(PDA) and polyaniline(PANI) as a kind of conductive polymers were employed as the NC precursor to yield the NC shell at high temperature. The NC materials is elaborately introduced into the Pt/C surface to not only restrain migration and dissolution of Pt NPs, but also act as the secondary active site supplier that imparting activity to the integral catalyst without blocking the inner Pt catalytic active sites.Firstly, we prepared the Pt/C@NC catalysts using “shape fixing via salt recrystallization” method. PDA as NC precursor polymerized in situ on the surface of Pt/C catalysts. Before graphitization, the Pt/C@PDA catalysts were fixed by Na Cl crystallization, which can limit the space of PDA, and reduce the generation of quaternary N with 3-D structure. The prepared Pt/C@NC catalysts exhibit a Pt mass and specific activity nearly 3.6 and 3.0 times higher than the commercial Pt/C catalysts. The accelerated durability test(ADT) shows that the Pt/C@NC catalysts only decreased ~15.43% in electrochemical surface area(ECSA), whereas the commercial Pt/C catalysts have lost 42.51% of their initial ECSA after 2000 CV.Secondly, we prepared Pt Fe@NC catalysts using Si O2 protection and PANI as precursor. After adsorbed Fe3+ ions, Pt/C catalysts coated with PANI and Si O2, and followed subjecting Pt/C@PANI@Si O2 to graphitization under at 800 oC to yield the NC shell. The prepared Pt Fe@NC catalysts with hollow nanostructure and evenly distributtion exhibit high activity and durability. The ORR onset potential and half-wave potentials measured on a Pt Fe@NC catalyst were only 48 and 18 m V behind that from commercial Pt/C catalyst respectively.