Characterization of the performance of CrN/Nb coated 316L stainless steel bipolar plates for PEMFC

• Published in: International journal of hydrogen energy Vol. 100; pp. 882 - 891
• Main Authors: Hou, Qiangqiang, Li, Xichao, Sun, Xianwei, Li, Shuo, Dai, Zuoqiang, Zheng, Lili, He, Yan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 27.01.2025
• Subjects: Coating; CrN/Nb; Electrochemical properties; Interfacial contact resistance; Metal bipolar plate; PEMFC; PEMFC; Electrochemical properties; Coating; CrN/Nb; Metal bipolar plate; Interfacial contact resistance
• ISSN: 0360-3199
• DOI: 10.1016/j.ijhydene.2024.12.384

Surface modification of metallic bipolar plates is a crucial subject for the performance elevation of proton exchange membrane fuel cells (PEMFCs). In this work, a series of CrN coatings and CrN/Nb coatings were prepared on SS316L by DC magnetron sputtering technology with different deposition power of 80 W, 100 W, 150 W and 200 W. The results show that with the decrease of deposition power, the surface of CrN/Nb coating changes from loose porous to uniform and dense, and the columnar crystal structure changes from burly to fine, which improves the corrosion resistance and electrical conductivity of the coating. The corrosion current density decreases from 3.5 μA cm−2 of CrN/Nb-200 W to 0.39 μA cm−2 of CrN/Nb-80 W. The XPS results show that the intensity of O–Cr peaks decreases while the intensity of N–Cr peaks increases with the decrease of power, which also confirms that the coatings prepared at low power have better corrosion resistance. Furthermore, the corrosion current density of CrN/Nb-80 W coated SS316L is 0.39 μA cm−2, and the interface contact resistance at 1.4 MPa is 9.2 mΩ cm2, which are much lower than those of CrN-80 W coated samples (1.58 μA cm−2 and 16.3 mΩ cm2). After the constant potential polarization test, the Fe and Cr ion concentrations in the solution of CrN/Nb coated specimens were significantly lower than those of CrN coated specimens, which indicates that the CrN/Nb coating has better corrosion resistance. The applying of Nb transition layer endows the coating and substrate better adhesion (increased 48%), which can hinder the penetrating cracks to the substrate in the coating and improve the corrosion resistance. •CrN and CrN/Nb coatings were deposited on the SS316L alloy under different powers.•The surface morphology becomes uniform and compact with decreasing the deposit power.•Coatings prepared at lower power possess better corrosion resistance and lower ICR.•The addition of Nb transition layer improves the performance of CrN coating.•Nb addition can hinder the columnar crystals growth of CrN.