Dealloying-Induced Zeolite-like Metal Framework of AB₂ Laves Phase Intermetallic Electrocatalysts

Abstract

Exploring an efficient and robust electrocatalyst for hydrogen evolution reaction (HER) at high pH and temperature holds the key to the industrial application of alkaline water electrolysis (AWE). Herein, we design an open tunnel structure by dealloying a series of Laves phase intermetallics, i.e., MCo 2 and MRu 0.25 Co 1.75 (M = Sc and Zr). The dealloying process can induce a zeolite-like metal framework for ScCo 2 and ScRu 0.25 Co 1.75 by stripping Sc metal from the center of a tunnel structure. This structural engineering significantly lowers their overpotentials at a current density of 500 mA/cm 2 (η 500 ) ca. 80 mV in 1.0 M KOH. Through a simple process, ScRu 0.25 Co 1.75 can be easily decorated on a carbon cloth substrate and only requires 132 mV to reach 500 mA/cm 2 . More importantly it can maintain activity over 1000 h in industrial conditions (6.0 M KOH at 333 K), showing its potential for practical industrial applications.

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

“…70 mV from 303 K (η 500 = 180 mV) to 333 K (η 500 = 110 mV). To the best of our knowledge, this outstanding HER activity of ZrCo 1.75 Rh 0.25 is the highest one among all the electrocatalysts reported so far. ,− More importantly, it can be operated at 300 mA/cm 2 over 400 h. In contrast, the HER performance of NbCo 1.75 Pt 0.25 decayed rapidly (an overpotential increase from 220 to 517 mV) over 150 h (Figure S18). This observation may be attributed to the original stability of intermetallic hosts (Figure S18) as there is a higher bonding state population of the Zr–Co bond than that of the Nb–Co bond at E F (Figure S19).…”

“…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. To be more precise, it is possible for one to adjust the d electron of the Pt metal with different populations (i.e., ZrCo 1.75 Pt 0.25 vs NbCo 1.75 Pt 0.25 ) and achieve the goal of being closer to the sweet spot.…”

Ahead by a Century: Discovery of Laves Phases Assisted by Machine Learning

“…High-entropy alloys are most frequently formed by Laves phases . Recently, “dealloyed” ScRu 0.25 Co 1.75 was shown to be an efficient electrocatalyst for hydrogen evolution …”