Ex situ and in situ evaluation of carbon ion-implanted stainless steel bipolar plates in polymer electrolyte membrane fuel cells

Abstract

The desirable properties of metallic bipolar plates in polymer electrolyte membrane fuel cells are good corrosion resistance and high electrical conductance. In this study, carbon-implanted SS316L stainless steel bipolar plates are evaluated by various ex situ and in situ methods. X-ray photoelectron spectroscopy and transmission electron microscopy reveal a carbon-enriched layer with a thickness of about 240 nm thick. The structure depends on the ion implantation fluence. The interfacial contact resistance and electrochemical behavior are determined using ex situ techniques. The interfacial contact resistance decreases with increasing ion implantation fluence. The results obtained by potentiodynamic tests, potentiostatic tests, and inductively coupled plasma optical emission spectrometry measurements are consistent with each other confirming that the corrosion resistance is significantly improved after carbon ion implantation. The carbon-implanted stainless steel bipolar plates are assembled into single cells to undergo in situ evaluation. The peak power density of the carbon-implanted bipolar plate increases from 566.5 mW cm −2 to 840.0 mW cm −2 and the power density at 0.6 V increases by a factor of two compared to those measured from a single cell made of unimplanted stainless steel bipolar plates.