Dual Ti and C ion-implanted stainless steel bipolar plates in polymer electrolyte membrane fuel cells

Abstract

The effects of dual Ti and C ion implantation on the corrosion resistance and surface conductivity of 316L stainless steel (SS) bipolar plates used in polymer electrolyte membrane fuel cells (PEMFC) are investigated. The ion-implanted SS bipolar plates are assembled into single cells to evaluate the performance and improvement. X-ray photoelectron spectroscopy (XPS) confirms the presence of the implanted layer and high-resolution transmission electron microscopy (HR-TEM) discloses an amorphous phase together with an underlying layer with fine grains on the surface of the Ti0.5C0.5 specimen due to ion collision. On the other hand, the surface microstructure of Ti0.5C2 consists of a precipitated nanophase layer, an amorphous underlying layer, and a zone with refined grains between the implanted surface and substrate. The interfacial contact resistance (ICR) of Ti0.5C0.5 is reduced by 6.5 times due to the Ti and C enriched surface and amorphous and fine grain underlayer. Electrochemical characterization and scanning electron microscopy (SEM) show reduced current density and improved corrosion resistance as a result of implantation of a proper ion fluence. According to the single cell evaluation, the peak power density of the ion-implanted bipolar plate increases from 566.5mWcm−2 to 709.8mWcm−2 and the power density at 0.6V increases by about 50% compared to those measured from the single cell assembled with unimplanted SS bipolar plates.