Ni cluster nucleation and growth on the anatase TiO2(101) surface: a density functional theory study

Abstract

Density functional theory (DFT) calculations are carried out to study the nucleation and growth rule of Ni clusters on both a perfect and defective anatase TiO₂(101) surface using supported Ni_n (n = 1–6) cluster models. Our results show that a single Ni atom prefers to adsorb at the bridge site formed by two-coordinated oxygen (2cO) atoms on the perfect TiO₂(101) surface and at the 3cO-bridge site on the defective TiO₂(101) surface. The active site for Ni cluster growth on the perfect TiO₂(101) surface shifts from the bridge site of two 2cO atoms or the 2cO–6cTi–3cO bridge site for Ni₁, Ni₂, and Ni₃ clusters to the 2cO–5cTi bridge site for Ni₄, Ni₅, and Ni₆. The Ni cluster cohesive energy remains constant with cluster size variation on both the perfect and defective surface. The Ni–TiO₂ interaction is the main driving force of the initial Ni nucleation stage, and the Ni–Ni interaction begins to control the Ni_n cluster growth process with increased cluster size.