Porous electrospun carbon nanofibers network as an integrated electrode@gas diffusion layer for high temperature polymer electrolyte membrane fuel cells

Abstract

High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) utilize phosphoric acid imbibed polybenzimide membranes, which allow for improved reaction kinetics due to the higher operating temperatures, but suffer from the corrosive environment and the sluggish oxygen transport and associated transport limitations. The latter issue is addressed in this work by the integration of the gas diffusion layer (GDL) into the gas diffusion electrode (GDE) in an entirely electrospun concept. For this purpose, coaxial electrospinning is applied by spinning two immiscible polymer solutions simultaneously to create a core-shell structure. Porous carbon felt structures are obtained due to phase separation in the shell and a subsequent carbonization treatment (integrated GDE@GDL). Full cell tests (0.6 mgPt cm−2) demonstrate a 21% increase in the power density normalized to the platinum content compared to the spray-coated reference (1 mgPt cm−2). Electrochemical impedance spectroscopy (EIS) measurements coupled with the distribution of relaxation times (DRT) analysis show that the morphology of the GDE@GDL favors oxygen transport inside the electrode. Mass transport limitations were successfully remedied by our electrospun concept rendering an additional GDL sheet obsolete.