Long-term Performance and Degradation of TiN-coated 304 Stainless Steel Bipolar Plates in Air-Breathing PEMFCs: A Comprehensive Evaluation

This study examines the performance of TiN-coated 304 stainless steel bipolar plates in air-breathing proton exchange membrane fuel cells (PEMFCs). A 1.0 mu m TiN coating was applied to SS304 and compared with graphite bipolar plates. Material characterization included impedance, contact resistance, water contact angle, and corrosion measurements. Long-term tests were conducted at 45 degrees C and 100 % relative humidity for hydrogen. Every 24 h, polarization curves and electrochemical impedance spectroscopy (EIS) were used to assess performance and degradation. A temperature-humidity control chamber and acidic environment were used to simulate fuel cell operating conditions. SEM and EDX spectra were applied to analyze coating degradation. Research results showed that TiN-coated SS304 had lower resistance, higher hydrophobicity, and greater corrosion resistance than uncoated SS304. The initial fuel cell performance was improved by 147 %, with a slower degradation rate due to a reduced ohmic resistance increase rate. After in a 3000-h simulated operation condition, a significant resistance changes were observed, and SEM/EDX spectra analysis revealed coating deterioration and substrate exposure. Overall, TiN coating significantly enhances the performance and durability of SS304 bipolar plates, making it a promising material for PEMFC applications.