(Digital Presentation) Graphene as Barriers to Prevent Phosphoric Acid Leaching in High-Temperature PEMFCs

Abstract

High-temperature PEMFCs running at 120-200℃ with the simplified water management has attracted more attention [1]. However, phosphoric acid molecules in polybenzimidazole membrane electrolyte (PA/PBI) are easily leaching to electrodes, which block pores of carbon fiber electrodes and impact gas transfer. Finally, the power density and durability of PEMFCs are extremely reduced [2].Graphene is a kind of two-dimensional (2D) structure of honeycomb lattice material and can block the penetration of almost all molecules and atoms, which is able to prevent PA molecules leaching as [3]. Our group has investigated a nitrogen-modified reduced graphene oxide (NrEGO) prepared by the electrochemical exfoliation, which has shown excellent performance in enhancing the activity and stability of catalysts [4]. Meanwhile, our previous research developed a single layer graphene loaded electrode. The power density of high-temperature PEMFCs is improved compared with commercial cells after accelerated stress test [5].Therefore, this work used NrEGO flakes as barriers to prevent phosphoric acid leaching to gas diffusion layer with lower Pt loading. In the present results, when the ratio of NrEGO and CB is 2 to 3 and the Pt loading is 0.25 mgPt/cm2, the cell improves 20% of the maximum power density and shows more stable with a decay of voltage by only 0.02 mV/h, which is quiet lower compared with that of 1.14 mV/h in commercial Pt/C.