Corrosion behavior of Ti-0.3Mo-0.8Ni (TA10) alloy in proton exchange membrane fuel cell environment: Experimental and theoretical studies

The Ti-0.3Mo-0.8Ni (TA10) alloy is a titanium-based material known for its favorable corrosion resistance, making it a promising candidate for PEMFC bipolar plates. In order to investigate the electrochemical behavior of the TA10 alloy in a simulated PEMFC environment, the microstructure of the alloy was characterized using scanning electron microscopy and X-ray diffraction. The corrosion resistance was evaluated through potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests in the simulated PEMFC cathode environment. Based on the experimental characterization, the mechanism underlying the improved corrosion resistance of the TA10 alloy in the PEMFC environment was revealed using first-principles calculations. The research findings demonstrate that the cast structure of the TA10 alloy comprises a predominant white & alpha;-phase matrix and a minor proportion of grayblack layered & beta;-phase. The & alpha;-phase is composed solely of 100 wt% Ti, while the & beta;-phase contains 90.4 wt% Ti and 9.6 wt% Ni. Under the simulated PEMFC environment, the corrosion potentials of TA1 and TA10 were observed to be - 0.424 V and - 0.228 V, respectively, in the anode environment, and - 0.382 V and - 0.234 V, respectively, in the cathode environment, representing an increase of approximately 38.7-46.2 % compared to the TA1 alloy. Importantly, the corrosion current density of the TA10 alloy was reduced by approximately 20.5-36.9 % compared to TA1, indicating enhanced corrosion resistance and chemical stability due to the higher corrosion potential and lower corrosion current density exhibited by the TA10 alloy. Furthermore, electrochemical impedance spectroscopy (EIS) measurements demonstrated a significant increase in the capacitive arc radius of TA10 compared to TA1, with an Rfb value of 7.166 k52 cm2 for TA10, approximately 13 times higher than the corresponding value of 0.529 k52/cm2 for TA1. This substantial increase in the Rfb value signifies the improved corrosion resistance of TA10 compared to TA1. Theoretical calculations revealed that the presence of Mo and Ni elements in the TA10 alloy effectively reduces the overpotential on the Ti surface. Specifically, the overpotential was found to be 0.734 eV for Ti-Mo, 0.569 eV for Ti-Ni, and when Mo and Ni were co-doped, the overpotential further decreased to 0.512 eV. This reduction in overpotential enhances the rate of the cathodic hydrogen evolution reaction and facilitates the formation of an anodic passivation film, thereby significantly improving the corrosion resistance of the TA10 alloy. In conclusion, our study provides comprehensive insights into the electrochemical performance of the TA10 alloy in a PEMFC environment, highlighting its potential as a corrosion-resistant material for bipolar plates in PEMFC applications.