Cr-implanted stainless steel bipolar plates in hydrogen fuel cells for enhanced electrical conductivity

Stainless steel is considered to be the most potential bipolar plate material in hydrogen fuel cells due to its thin thickness and low cost, but suffers from decreased electrical conductivity in long-time usage. Herein, the surface of 316L stainless steel (SS316L) is modified by the ion implantation of Cr with different accelerating voltages and ion implantation doses. The implantation of Cr brings in a substantial improvement in the surface electrical conductivity, which is due to the formation of Cr oxide, Cr7C3 and Cr23C6. In all cases, interfacial contact resistance (ICR) is decreased with the increased implantation doses. In the cathodic environment, the minimum value of ICR (14.89 m omega center dot cm(2)) is obtained at an accelerating voltage of 20 kV. However, in the anodic environment, the minimum value of ICR (7.19 m omega center dot cm(2)) is obtained at an accelerating voltage of 40 kV. This is because the passive layer is destroyed by hydrogen. Besides, the deeper distribution of the Cr7C3 and Cr23C6 facilitates the formation of a more stable conductive pathway, which decreases the ICR. Moreover, simulations are also performed to give atomistic insights into the radiation damage during the implantation process. The results show that the maximum radiation damage is caused at an accelerating voltage of 40 kV. The unveiled mechanisms of the modified layer in this work are expected to guide the surface modification of stainless steel bipolar plates.

Automated summary

The surface conductivity of 316L stainless steel is improved by the ion implantation of Cr, which leads to the formation of Cr oxide, Cr7C3, and Cr23C6. The interfacial contact resistance decreases with increasing implantation doses. In the cathodic environment, the minimum ICR is obtained at an accelerating voltage of 20 kV, while in the anodic environment, the minimum ICR is obtained at an accelerating voltage of 40 kV. The deeper distribution of Cr7C3 and Cr23C6 facilitates the formation of a more stable conductive pathway, reducing the ICR.