Al atom on MoO₃(010) surface: adsorption and penetration using density functional theory

Abstract

Interfacial issues, such as the interfacial structure and the interdiffusion of atoms at the interface, are fundamental to the understanding of the ignition and reaction mechanisms of nanothermites. This study employs first-principle density functional theory to model Al/MoO3 by placing an Al adatom onto a unit cell of a MoO3(010) slab, and to probe the initiation of interfacial interactions of Al/MoO3 nanothermite by tracking the adsorption and subsurface-penetration of the Al adatom. The calculations show that the Al adatom can spontaneously go through the topmost atomic plane (TAP) of MoO3(010) and reach the 4-fold hollow adsorption-site located below the TAP, with this subsurface adsorption configuration being the most preferred one among all plausible adsorption configurations. Two other plausible configurations place the Al adatom at two bridge sites located above the TAP of MoO3(010) but the Al adatom can easily penetrate below this TAP to a relatively more stable adsorption configuration, with a small energy barrier of merely 0.2 eV. The evidence of subsurface penetration of Al implies that Al/MoO3 likely has an interface with intermixing of Al, Mo and O atoms. These results provide new insights on the interfacial interactions of Al/MoO3 and the ignition/combustion mechanisms of Al/MoO3 nanothermites.

Nanoscale surface reactions by laser irradiation of Al nanoparticles on MoO3 flakes

“…While step edges are common along the 〈001〉 direction of α-MoO 3 [19], these were not observed near the reaction zones. Based on the proposed sub-surface Al adsorption mechanism, Al atoms adsorb into the interstitial sites between adjacent terminal oxygen sites on the face of MoO 3 , minimally altering the bond length within the MoO 3 host [28]. Such a mechanism would produce an unperceivable change in surface topology, consistent with our observations.…”

“…Previous density functional theory (DFT) studies by others have investigated the interaction of atomic Al with the α-MoO 3 lattice. Wu et al examined the adsorption energy of individual Al adatoms at various sites along the (010) crystalline plane of α-MoO 3 [28]. This study showed that subsurface adsorption of an Al atom is more stable than surface adsorption, and that Al sub-surface adsorption occurs preferentially between terminal oxygen pairs in the 〈001〉 direction.…”

Sulfur-Resistant Ceria-Based Low-Temperature SCR Catalysts with the Non-bulk Electronic States of Ceria

“…In fact, on the exposed MoO 3 (010) surface, there are abundant four-fold hollow sites formed by four surface lattice oxygen atoms (Figure S1c). 22 These hollow sites are suitable for anchoring Ce 3+/4+ ions with an ionic radius of ∼1 Å. 23 Moreover, the loading of ceria is lower than the monolayer on the surface of MoO 3 calculated from its external specific surface area of ∼7 m 2 g −1 .…”

Using a Thin ZnO Film as an Intermediate Layer to Tune the Performance of Mg-Based Nanolaminates: A First-Principles Study

“…Lanthony et al investigated the initial oxidation of the Al(111) surface after CuO deposition and revealed the formation mechanisms of alumina and copper condensation in the bulk. Wu et al studied the adsorption of Al atoms on the MoO 3 (010) surface and found the initial mixture of Al, Mo, and O atoms. Gao et al disclosed the interactions between the Al adatom and the ZnO surface through a combination of experiments and theoretical calculations.…”