Abstract
Austenitic stainless steel has been researched as a promising candidate material for bipolar plates in proton exchange membrane fuel cells. However, its interfacial contact resistance (ICR) is about 16 times higher that of the Department of Energy (DOE) target (10 mΩ cm2), which leads to undesirable fuel cell performance. In this work, a new hybrid plasma surface engineering process, based on active screen plasma co-alloying, has been developed to simultaneously alloy 316 austenitic stainless steel (316 SS) surfaces with both nitrogen and niobium. The results demonstrated that the layer structure of the modified surfaces can be tailored by adjusting the treatment conditions. All the plasma treated 316 SS samples exhibited significantly reduced ICR below the DOE target of 10 mΩ cm2. The corrosion resistance of the N/Nb co-alloyed 316 SS was much better than active screen plasma nitrided and marginally better than the untreated material.
Highlights
As an efficient, clean and quite power source, proton exchange membrane fuel cells (PEMFCs) have received extensive interest in the last decade mainly due to the concerns over severe air pollution caused by conventional power sources and the depletion of fossil energies
This paper reports a new hybrid plasma surface technology which combines low-temperature active screen plasma co-alloying with both nitrogen and niobium with deposition of a thin surface niobium layer on the top
The results of interfacial contact resistance (ICR) measurement revealed that the ICR values of all the ASPA(N þ Nb) samples were around 9 mU cm2 and their difference was within the range of the experimental error
Summary
Clean and quite power source, proton exchange membrane fuel cells (PEMFCs) have received extensive interest in the last decade mainly due to the concerns over severe air pollution caused by conventional power sources and the depletion of fossil energies. Significant improvement has been made recently in the efficiency and performance of PEMFCs. the wide commercial application of PEMFCs has been retarded, to a large extent, by the low mechanical strength and the high fabrication cost of graphite bipolar plates [1]. There are still some limitations of austenitic stainless steels and technical challenges to be addressed Their insufficient corrosion resistance [11,12] and poor conductivity due to the formation of passive oxide layer [13,14] can lead to undesired degradation of the power output of PEMFCs. It is known that surface modification has been successfully used to improve the surface properties of materials and components. It could be a promising method to improve the surface conductivity and/or corrosion resistance of stainless steel bipolar plates [15e18]
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