Effect of Single-Layer MoS₂on the Geometry, Electronic Structure, and Reactivity of Transition Metal Nanoparticles

Abstract

We present results of ab initio density functional theory (DFT) based calculations of the geometry, electronic structure, and reactivity of subnanometer-sized (29-atom) transition metal nanoparticles (NPs) (Cu29, Ag29, and Au29) supported on single-layer MoS2. As compared to its pristine form, defect-laden MoS2 (with a S vacancy row) has relatively larger effect on the above properties of the NPs. The NPs bind more strongly on defect-laden than on pristine MoS2 (in the order Cu29 > Ag29 > Au29), confirming the important role of vacancies in stabilizing the NPs on the support. The presence of vacancies also leads to an increase in charge transfer from the NPs to MoS2 (with the same elemental trend as for their binding energy) and to a shift of the d-band center of the NPs further toward the Fermi level, in turn influencing their propensity toward chemical activity. We examine the adsorption and dissociation of O2 as the prototype reactions and find that there is no barrier for O2 to adsorb on top of an atom at the NP apex, where the frontier orbitals are localized, and that the dissociation channel proceeds through a chemisorbed state. The presence of the support leads to increase in the number of sites at which O2 can adsorb with similar binding energy (<0.1 eV difference). Interestingly, energy barriers for both dissociation and recombination of O2, when adsorbing at the NP apex, increase in the presence of the MoS2 support. However, since the increase in the barrier for recombination is much larger than for dissociation, the latter should be more favored. In particular, for defect-laden MoS2 supported Au29 the recombination faces a barrier of 1.36 eV whereas the dissociation does 0.5 eV, implying that the defect-laden support may significantly improve the catalytic performance of Au29 toward oxidation reaction.

Gold Dispersion and Activation on the Basal Plane of Single-Layer MoS2

“…51 These results are also in agreement with the wellestablished inactivity of bulk gold and the findings of Ref. 21 for O 2 adsorbates. The computational approach also allows us to compare the binding energy of CO molecules on gold clusters supported by MoS 2 to CO binding to unsupported gold clusters of the same shape.…”

“…Our findings confirm the computational predictions of Rawal et al 21 that suggest Au nanoparticles to bind strongly to single-layer MoS 2 ; Rawal et al 21 underscore the potential of the Au/MoS 2 materials system for catalytic application. Furthermore, unlike several prior studies that define the impact of the substrate on the catalytic activity as indirect, i.e.…”

DFT calculations of the structure and stability of copper clusters on MoS2

“…The adsorption of metal species on semiconducting supports such as 2D monolayers of MoS 2 is a subject of significant interest in a range of applications, particularly in catalysis and, more recently, in semiconductor nanodevices where 2D materials can function as barrier materials to prevent copper diffusion into the underlying dielectric material. While there have been studies of single-atom adsorption at MoS 2 [26,29] and the adsorption of larger nanoclusters of noble metals, [25] there is as yet no comprehensive study of the interactions of small subnanometer metal species with a MoS 2 ML, which is useful to probe the fundamental metal-MoS 2 interactions. In this study, we investigated the adsorption behaviour of small Cu n nanoclusters (n = 1-4) through first-principles density functional theory.…”

“…There have been numerous computational studies of MoS 2 and other 2D materials [9,22,23], many of which have examined the adsorption of, or doping with, various elements including transition metals [3,9,[24][25][26][27][28], alkali and alkaline-earth metals [29][30][31] as well as non-metals such as H, B, C, O and N [31]. Work involving atom adsorption on 2D materials can generally be divided into two categories: single-atom adsorption [26,[29][30][31] and adsorption of larger structures such as nanoparticles [25] or metal chains [24].…”

“…Despite slightly contradictory results depending on the computational setup, the authors conclude that the adsorption of noble metal chains allows for a small opening of the bandgap of graphene, although they are unable to interpret the exact mechanism by which this occurs. The adsorption of 29 atom nanoparticles of Cu, Ag and Au on a MoS 2 monolayer is presented by Rawal et al [25] to study the effect of defects in MoS 2 on the catalytic activity of the supported nanoparticles. They observe that the magnitude of binding energy and charge transfer follows the trend Cu > Ag > Au.…”