Molybdenum carbide coated 316L stainless steel for bipolar plates of proton exchange membrane fuel cells

Superior corrosion resistance and high electrical conductivity are crucial to the metallic bipolar plates towards a wider application in proton exchange membrane fuel cells. In this work, molybdenum carbide coatings are deposited in different thicknesses onto the surface of 316 L stainless steel by magnetron sputtering, and their feasibility as bipolar plates is investigated. The microstructure characterization confirms a homogenous, compact and defectless surface for the coatings. The anti-corrosion performance improves with the increase of the coating thickness by careful analysis of the potentiodynamic and potentiostatic data. With the adoption of a thin chromium transition layer and coating of a similar to 1052 nm thick molybdenum carbide, an excellent corrosion current density of 0.23 mu A cm(-2) is achieved, being approximately 3 orders of magnitude lower than that of the bare stainless steel. The coated samples also show a low interfacial contact resistance down to 6.5 m Omega cm(2) in contrast to 60 m Omega cm(2) for the uncoated ones. Additionally, the hydrophobic property of the coatings' surface is beneficial for the removal of liquid water during fuel cell operation. The results suggest that the molybdenum carbide coated stainless steel is a promising candidate for the bipolar plates. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.