Manipulating the Magnetic Moment of Palladium Clusters by Adsorption and Dissociation of Molecular Hydrogen

5 years ago

Manipulating the Magnetic Moment of Palladium Clusters by Adsorption and Dissociation of Molecular Hydrogen

Maite Alducin, María J. López, Julio A. Alonso, María Blanco-Rey, J. Iñaki Juaristi

There is a sizable probability for the dissociation of H₂ deposited at low energy on palladium clusters supported on graphene. This is accompanied by a total or partial quenching of the magnetic moment of the cluster, and we have investigated the interplay between these two processes: magnetization change and molecular dissociation. For this purpose, the density functional formalism has been used, in the form of ab initio molecular dynamics simulations and static calculations. Two different cluster sizes have been investigated, Pd₆ and Pd₁₃, and the conclusion is that the size of the Pd cluster has a strong influence on the sequence of these two processes. The effect of H₂ dissociation is to reduce the magnetic moments of both clusters by about 2 μ_B, resulting in unpolarized Pd₆ on the one hand and Pd₁₃ with a magnetic moment of 2 μ_B on the other. In the case of Pd₆, the quenching of the magnetic moment occurs immediately after the dissociation of the H₂ molecule. In contrast, the quenching of the magnetic moment in Pd₁₃ is induced by the arrival of the H₂ molecule at its preferred adsorption sites on specific Pd atoms. Once settled in those positions, dissociation takes place almost spontaneously, with a very small activation barrier and no further change of the magnetization. In this way, adsorption and dissociation of H₂ can be viewed as an effective tool to manipulate the magnetic state of clusters and nanoparticles supported on carbonaceous substrates, which could lead to interesting applications in devices.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b03996

DOI: 10.1021/acs.jpcc.7b03996