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. 2022 Oct 3;7(42):37379-37387.
doi: 10.1021/acsomega.2c04107. eCollection 2022 Oct 25.

Density Functional Study of Size-Dependent Hydrogen Adsorption on Ag n Cr (n = 1-12) Clusters

Ngo Thi Lan  1   2 , Nguyen Thi Mai  1 , Ngo Tuan Cuong  3 , Phung Thi Hong Van  4 , Duong Duc La  5 , Nguyen Minh Tam  6   7 , Son Tung Ngo  6   7 , Nguyen Thanh Tung  1
Affiliations

Density Functional Study of Size-Dependent Hydrogen Adsorption on Ag n Cr (n = 1-12) Clusters

Ngo Thi Lan et al. ACS Omega. .

Abstract

Increasing interest has been paid for hydrogen adsorption on atomically controlled nanoalloys due to their potential applications in catalytic processes and energy storage. In this work, we investigate the interaction of H2 with small-sized Ag n Cr (n = 1-12) using density functional theory calculations. It is found that the cluster structures are preserved during the adsorption of H2 either molecularly or dissociatively. Ag3Cr-H2, Ag6Cr-H2, and Ag9Cr-H2 clusters are identified to be relatively more stable from computed binding energies and second-order energy difference. The dissociation of adsorbed H2 on Ag2Cr, Ag3Cr, Ag6Cr, and Ag7Cr clusters is favored both thermodynamically and kinetically. The dissociative adsorption is unlikely to occur because of a considerable energy barrier before reaching the final state for Ag4Cr or due to energetic preferences for n = 1, 5, and 8-12 species. Comprehensive analysis shows that the geometric structure of clusters, the relative electronegativity, and the coordination number of the Cr impurity play a decisive role in determining the preferred adsorption configuration.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
(Color online) Optimized structures of AgnCr, AgnCr–H2, and AgnCr–2H clusters (n = 1–12). The light blue, violet, and red spheres represent Ag, Cr, and H atoms, respectively.
Figure 2
Figure 2
(Color online) (a) Binding energy per atom (Eb) and (b) second-order energy difference (Δ2E) of AgnCr–H2 and AgnCr–2H clusters.
Figure 3
Figure 3
(Color online) DOS of AgCr–H2, Ag5Cr–H2, and Ag8Cr–H2 clusters. HOMO and LUMO stand for highest occupied molecular orbitals and lowest unoccupied molecular orbitals, respectively.
Figure 4
Figure 4
(Color online) Calculated reaction pathways and relative Gibbs free energies (ΔG298K in eV) for the molecular and dissociative adsorption of H2 on (a) Ag2Cr, (b) Ag3Cr, and (c) Ag6Cr. The intermediates and TSs are denoted as Ii and TSi. Light blue, violet, and red spheres represent Ag, Cr, and H atoms, respectively.
See this image and copyright information in PMC

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