Balance between Activity and Stability of Single Metal and Intermetallic Compounds for Electrocatalytic Hydrogen Evolution Reaction

Abstract

The higher population of the antibonding state around the Fermi level will result in better activity yet lower stability of HER (Re vs Ru metal). There seems to be a limitation or balance for using a single metal since the bonding scheme of a single metal is relatively simple. Combining Re (strong bonding), Ru (HER active), and Zr metal (corrosion-resistant) grants ternary intermetallic compound ZrRe1.75Ru025, exhibiting excellent HER activity and stability in acidic and alkaline electrolytes. The overpotential at a current density of 10 mA/cm2 (η10) for ZrRe1.75Ru025 is much lower compared to that of ZrRe2. Although the HER activity of ZrRe1.75Ru025 is not comparable to that of ZrRu2, it demonstrates outstanding HER stability, while the current density of ZrRu2 is over ca. 16% after 6 h. This suggests that intermetallic compounds can break the constraint between activity and stability in a single metal for HER, which may be applied in other fields as well.

Correlation between d Electrons and the Sweet Spot for the Hydrogen Evolution Reaction: Is Platinum Always the Best Electrocatalyst?

“…The Laves phase (general formula AB 2 ) is an excellent candidate to testify the assumption mentioned above because nearly all transitional metals can form this phase with appropriate chemical combinations. , Consequently, ZrCo 2 and NbCo 2 , two Laves intermetallic compounds, were used as the host with the incorporation of a small amount of group VIII transition metals to fabricate two series, namely, ZrCo 1.75 M 0.25 and NbCo 1.75 M 0.25 ( M = Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt). The main reason we select the Zr and Nb systems for comparison is because the electronegativity of Zr is lower than that of Nb (χ Zr = 1.33; χ Nb = 1.60, Pauling scale). , The Co or M element in ZrCo 1.75 M 0.25 will receive more electron (i.e., higher d electron population) than that of NbCo 1.75 M 0.25 (Figure a), which allows us to investigate the correlation between the d electron population and the corresponding HER activity.…”