Corrosion Resistance and Conductivity of Ta-Nb-N-Coated 316L Stainless Steel as Bipolar Plates for Proton Exchange Membrane Fuel Cells

The large-scale application of stainless steel (SS) bipolar plates (BPs) in proton exchange membrane fuel cells (PEMFCs) is mainly limited by insufficient corrosion resistance and electrical conductivity. In this work, Ta-Nb-N coatings were prepared on 316L SS substrates by unbalanced magnetron sputtering to improve corrosion resistance and conductivity. The Ta-Nb-N coatings had a dense structure without obvious defects. In simulated PEMFC cathode environments consisting of 0.5 M H2SO4 + 2 ppm HF at 70 +/- 0.5 degrees C, which is harsher than the U.S. Department of Energy specification, the corrosion current density of Ta-Nb-N-coated BPs was reduced to 2.2 x 10-2 mu A<middle dot>cm-2. Ta-Nb-N-coated samples showed better electrical conductivity than 316L SS, which had an excellent interfacial contact resistance of 9.2 m Omega<middle dot>cm2. In addition, the Ta-Nb-N-coated samples had a water contact angle of 100.7 degrees, showing good hydrophobicity for water management. These results indicate that Ta-Nb-N coatings could be a promising material for BPs.