The Study On Graphite Nano-Fiber As Supporter Of Catalysts For PEMFC

Proton exchange membrane fuel cells (PEMFCs) are promising in both stationary power generation and as vehicular power sources due to their high operational efficiencies, ambient operation conditions and exceptional clean environments. However, one challenge for the commercialization of PEMFC is to improve lifetime.Carbon support plays a key role in PEMFC and has attracted significant attention in recent researches. The durability of PEMFCs has been recently recognized as one of the most important issues to be addressed before the commercialization of the PEMFCs. It is believed that excessive degradation of stack voltage is the major failure mode for fuel cell systems. Among the reasons for the voltage degradation, Pt surface area loss due to carbon support corrosion and Pt dissolution/aggregation is considered one of the major contributors. In the state of the art PEMFC, Vulcan XC-72(XC-72) is normally used as catalyst support material for PEMFCs. Despite its widespread use, carbon is known to undergo electrochemical oxidation to surface oxides, and eventually to CO2 or CO at the cathode of a fuel cell, where it is subject to high acidity, high potential, high humidity, and high temperature (80℃). Furthermore, during the start-up and shutdown of a fuel cell, local cathode potential can reach as high as 1.5V, which significantly speeds up the carbon corrosion. As carbon is corroded away, noble metal nanoparticles will be lost from the electrode or aggregated to larger particles. One strategy to reduce performance degradation due to carbon corrosion is to use alternative more stable carbon support.In this paper, Graphite nano-fiber(GNF) was prepared by using high-energy ball mill. The morphology and structure of which were explored with TEM. The electrochemical stability of GNF supported and XC-72 supported Pt (Pt/C and Pt/GNF) electrodes was investigated using potentiostatic oxidation. The peak current is only enhanced by 2% for GNF while 60% for XC-72 under same conditions. XC-72 shows 40% more corrosion current than GNF. Almost 84.7% of Pt surface area was lost for XC-72 after 60h oxidation treatment, while only 37.2% loss is observed for GNF, indicating that GNF could potentially provide much higher durability than XC-72. By comparing the electrochemical properties of GNF with XC-72, it is found that the use of GNF can be promising in effectively reducing the carbon corrosion problem.