Platinum nanoparticles supported on nitrogen and fluorine co-doped graphite nanofibers as an excellent and durable oxygen reduction catalyst for polymer electrolyte fuel cells

Nitrogen and fluorine co-doped graphite nanofibers (NF-GNFs) are explored as highly corrosion-resistant support materials and investigated for their possible interaction with Pt as an efficient oxygen reduction reaction (ORR) catalyst in an acidic medium. The Pt/NF-GNF catalyst exhibits enhanced ORR behavior with greater electrochemical stability, which is exclusively attributed to the simultaneous presence of N and F heteroatoms, which induces charge delocalization in the GNF matrix based on the electronegativity difference between carbon and heteroatoms. This facilitates a uniform deposition of Pt nanoparticles over NF-GNFs and interaction between Pt nanoparticles and the GNF support matrix. The Pt/NF-GNF catalyst was subjected to 10,000 repeated potential cycles between 0 and 1.05 V in acidic media, resulting in a 30-mV loss in ORR activity, compared to the activity loss of about 200 mV for commercial Pt/C catalysts. The carbon corrosion and catalyst stability are also determined with more stringent corrosive test cycles, that is, maintaining the potential of the cell as high as 1.4 V for 180 s and later decreasing it to 0.6 V for 30 s versus reversible hydrogen electrode (RHE) for 500 cycles, mimicking the actual conditions of operating fuel cells. Under these harsh corrosive conditions, the Pt/NF-GNF catalyst displayed excellent stability with only a 90-mV loss in E-1/2 in relation to the 270-mV loss in E-1/2 for commercial Pt/C catalysts. While evaluating the performance of the Pt/NFeGNF catalyst in a polymer electrolyte membrane fuel cell (PEMFC), a peak power density of 867 mW cm(-2) was achieved with a minimal Pt loading of 0.1 mg cm(-2), which demonstrates the potential application of this catalyst as a cathode catalyst in fuel cell reactions. (C) 2016 Elsevier Ltd. All rights reserved.