Vibrational study of CO, O2, and H2 Adsorbed on the CoCrFeNi (110) High Entropy Alloy Surface

Document Type

Article

Publication Date

8-29-2024

Abstract

The vibrational properties of CO, O2, and H2 molecularly or dissociatively adsorbed on a CoCrFeNi(110) surface have been probed using high-resolution energy loss spectroscopy (HREELS) and modeled using density functional theory (DFT) calculations. Large (∼20 mm3) single-crystal, quaternary face-centered cubic CoCrFeNi was synthesized via a modified Czochralski technique. We show strong evidence that CO adsorbs primarily on bridge and on-top sites in compositionally varied local environments, which reflect the random, multielemental surface composition inherent in a high entropy alloy. A variation of adsorption sites is also found with oxygen, which exhibits two broad groups of modes. Comparison to previous photoemission and theoretical studies suggests that the higher energy modes consist primarily of local CrOx species, while the lower energy modes are due to oxygen atoms adsorbed on other metal sites. Unlike CO and O2, HREELS upon H2 adsorption shows only two much narrower modes and is consistent with atomic adsorption on 3-fold hollow sites. The hypothesized adsorption sites for all three species are directly corroborated by our DFT calculations.

Publication Source (Journal or Book title)

Journal of Physical Chemistry C

First Page

14315

Last Page

14325

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