Theoretical Screening of Transition Metal Alloys with High Corrosion Resistance: The Case of Ta-Based Alloys as an Example

Proton exchange membrane water electrolysis (PEMWE) is one of the potential strategies to generate green hydrogen energy, and anticorrosive coatings are mandatory to protect the bipolar plates, an important component of PEMWE. However, it is still challenging to explore the high-corrosion-resistance coatings by trial and error. In this paper, the corrosion properties of Ta and its alloys as examples are studied theoretically; in particular, the influences of crystal planes and alloying elements on the corrosion resistance have been studied systematically. Four descriptors, surface energy density ξ, work function τ, electronic descriptor ψ, and d band center ς, are proposed to screen the high-corrosion-resistance coatings. It is found that the electronic descriptor ψ can well predict the atomic escape energy and thus the corrosion resistance of Ta-based binary alloys with the coefficient of determination R² of 0.804 and 0.949, respectively. Among them, TaW and TaCr alloys exhibit the most excellent corrosion resistance with the lowest I_corr (<1.59 × 10^-7 A cm^-2) and the highest U_corr (> −0.011 V vs SHE) because of the largest −IpCOHP values and thus the strongest binding strength. The screening method is also applicable to the other alloys.