Enhancing electrochemical and passive behavior of Ti-based medium entropy alloys in proton exchange membrane water electrolysis anodic environment through Zr and Nb synergy

Abstract

The synergistic effect of Zr and Nb on the passive behavior of non-equiatomic Zr-Ti-Nb as bipolar plates in proton exchange membrane water electrolysis (PEMWE) was investigated. The experiment revealed that the complementary change of Zr and Nb content resulted in the corrosion resistance sequence of Z40 > Z20 > Z26 > Z34. The primary constituents of the passive films predominantly comprised ZrO2, TiO2, and Nb2O5. The relative content of ZrO2 and Nb2O5 exceeded the atomic proportions of Zr and Nb in the substrate. Additionally, higher potentials had a significant impact on reducing the number of point defects in the passive films while increasing their thickness. The addition of Zr and Nb inhibited the formation of defects in the passive film. The study also investigated operation-induced passive behaviors. Accelerated stress tests were conducted using two square ripple potentials to simulate overload operating conditions. The findings indicated that the lower upper limit potential was insufficient to establish stable passivation.