Potential polarization accelerated degradation of interfacial electrical conductivity for Au/TiN coated 316L SS bipolar plates used in polymer electrolyte membrane fuel cells

Highlights: • Increase of ICR of Au/TiN/SS under various potential polarization conditions is studied. • Dissolution processes of Au Au/TiN/SS at different polarization modes is analyzed. • Probability of electrically contact between Au dots and carbon fiber is calculated. • Dependence of ICR on surface coverage of Au dots (Au%) is discussed. • A threshold value of 4∼6% Au dots to achieve the target ICR is established. Influence of four types of potential polarization on the interfacial contact resistance (ICR) of Au/TiN coated 316 L SS bipolar plates used in polymer electrolyte membrane fuel cells is investigated. Au/TiN coating gives superior small ICRs under single potentiostatic or cyclic potentiodynamic polarization, demonstrating great potential for commercial application. However, cyclic combined polarization induces significant delamination of Au dots, and thus Au/TiN/SS exhibits a remarkable increase of ICR. Analysis of ICR and its dependence on Au dots suggest that 4–6% of Au surface coverage is the critical threshold value for Au/TiN coated metal bipolar plates to achieve the target of ICR.