DFT investigation of Au_nMo (n = 2-12) clusters: the barrierless hydrogen adsorption behavior of Au₉Mo

Bimetallic gold-molybdenum clusters have attracted considerable attention for their potential in hydrogen-related applications, including catalysis and energy storage. In this study, we employ density functional theory to systematically investigate the interaction of H₂ with small Au_nMo clusters (n = 2-12). Our findings reveal that the cluster geometries remain stable upon both molecular and dissociative adsorption of H₂. The preferred adsorption configuration arises from a balance of factors including the adsorption site (surface vs. encapsulated Mo), electronegativity difference, and atomic coordination. Dissociative adsorption is identified to be both thermodynamically and kinetically favorable for n = 6, 8, and 9 species. With a submerged barrier of 0.04 eV for activating the hydrogen dissociation process, Au₉Mo exhibits potential as a hydrogen storage and catalytic material. In contrast, significant energy barriers hinder dissociative H₂ adsorption on Au₅Mo and Au₇Mo, while clusters with n = 2-4 and 10-12 exhibit a thermodynamic preference for molecular adsorption.