Designing Partially Coated Ultrathin Hydrophobic Silica Layer for Highly Conductive and Durable Carbon Nanofiber as Cathode Carbon Support in Polymer Electrolyte Fuel Cells

Abstract

For the last decade, the polymer electrolyte fuel cells (PEFCs) have been recognized as a strong alternative power source instead of the gasoline-powered internal combustion engine due to their high energy conversion efficiency and environmental benignity. Among a number of composition factors, the development of cathode electrode with affordable durability is arguably the most important consideration for maintaining long-term automotive applications because their performances are typically limited by permanently damaged carbon supports and platinum (Pt) loss during abnormal and transient conditions such as very fast potential transient condition and frequent start-up/shutdown procedures. In the carbon corrosion procedures, it is important to have an appropriate strategy that provides means to significantly reduce the carbon corrosion as follows: i) there are fewer water molecules in the vicinity of carbon supports to decrease the carbon corrosion and Pt oxidation formation according to mechanism of electrochemical carbon corrosion; and ii) the spill-over of ∙OH radical from Pt particles should be minimized by avoiding the direct contact between oxidized Pt and carbon surface. Herein, we reported a new strategy to functionalize the graphitized platelet carbon nanofiber (PCNF) surface, which was developed to make an unevenly-coated ultrathin hydrophobic silica layer on PCNF. Subsequently, Pt nanoparticles would be deposited into an empty space between an unevenly-coated silica layers. According to the experimental observation related to the electrochemical reactions, the initial performance of membrane electrode assembly (MEA) based on PCNF composite with 5 wt% silica layer exhibited similar to that for virgin PCNF due to similar HFR values. To the best of our knowledge, its initial cell performance is one of the best among the PCNF composites with silica layer reported in the literature. In addition, the PCNF composite with silica layer showed superior long-term durability compared to the virgin PCNF due to enhanced durability of carbon support and Pt nanoparticles.