Corrosion properties and cell performance of CrN/Cr-coated stainless steel 316L as a metal bipolar plate for a direct methanol fuel cell

CrN/Cr-coated stainless steel (STS) 316L is investigated as the material for a metal bipolar plate for a direct methanol fuel cell (DMFC) under actual operating circumstances. Protective coating layers of CrN/Cr are formed on STS 316L using an unbalanced magnetron (UBM) DC sputter via Cr target in an effort to improve the corrosion resistance and long-term stability of the STS 316L. In a corrosion resistance test, the CrN/Cr-coated STS 316L shows much better corrosion resistance than bare STS 316L in simulated electrolytic environments under anodic and cathodic potentials relevant to DMFCs. The interfacial contact resistance (ICR) between CrN/Cr-coated 316L and carbon paper decrease to 4 mΩ cm² at a compaction force of 150 N cm⁻² compared to bare STS 316L (570 mΩ cm²). The CrN/Cr-coated STS 316L cell has better cell performance compared to the bare STS 316L cell. Furthermore, the CrN/Cr-coated STS 316L cell exhibit low voltage losses of 38.2 μV h⁻¹ under long-term operation of 760 h. These results show that the CrN/Cr-coated STS 316L, demonstrating its feasibility for use as a metal bipolar plate in a DMFC under actual operating circumstances.