Performance of Ti–Ag-deposited titanium bipolar plates in simulated unitized regenerative fuel cell (URFC) environment

Titanium with excellent corrosion resistance, good mechanical strength and lightweight is an ideal BPP material for unitized regenerative fuel cell (URFC), but the easy-passivation property accordingly results in poor cell performance. Surface modification is needed to improve the interfacial conductivity. In this study, Ti–Ag film is prepared on TA1 titanium as bipolar plates for URFC by pulsed bias arc ion plating (PBAIP). Interfacial conductivity of Ti–Ag/Ti is improved obviously, presenting an interfacial contact resistance of 4.3 mΩ cm2 under 1.4 MPa. The results tested by potentiodynamic, potentiostatic and stepwise potentiostatic measures in simulated URFC environments show that Ti–Ag/Ti has good anticorrosion performance, especially at high potential. The corrosion current density of Ti–Ag/Ti is approximately 10−5.0 A cm−2, similar to that of uncoated titanium, at 2.00 V (vs. NHE) in a 0.5 M H2SO4 + 5 ppm F− solution at 70 °C with pressured air purging. Ti–Ag/Ti sample also has low surface energy. The contact angle of the sample with water is 102.7°, which is beneficial for water management in URFC. The bipolar plate with cost-effective Ti–Ag film combines the prominent interfacial conductivity with the excellent corrosion resistance at high potential, showing great potential of application in URFC.