The very recent development of highly selective experimental techniques making possible the synthesis of subnanometer-sized metal clusters is pushing our understanding of these quantum materials far beyond the present knowledge in materials science. When the size of a metal cluster is reduced to a small number of atoms, the d-band of the metal splits into a subnanometer-sized network of discrete molecule-like d orbitals, with the inter-connections having the length of a chemical bond (1-2 Angs.). The spatial structures of the molecular orbitals of these small clusters make all the metal atoms cooperatively active and accessible, leading to their structural fluxionality, and appearance of their novel properties and outstanding stability. By presenting specific applications, I will illustrate how state-of-the-art first principles modelling, when combined with cutting-edge synthesis (wet chemical) procedures and experimental caracterization techniques, is helping us to shape this modern field of subnanometer science. After briefly outlining our computational approaches, I will show how modified TiO2 surfaces with Cu5 and/or Ag5 atomic quantum clusters can be visible-light photo-active materials, potential photocatalysts for CO2 reduction, and hosts of multiple surface polarons. Moreover, I will also explain how extended first principle modelling of Ag5-modified TiO2 surfaces has provided new relevant fundamental insights into a general polarization phenomenom accompanying the formation of surface polarons, agreeing very well with the experimental observations through X-ray absorption near edge structure (XANES) spectroscopy.

First principles modelling of TiO2-supported subnanometer-sized metal clusters: From clean energy sources to 2D polaronic materials

ACS Spring Meeting 2021

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