Abstract
We perform first-principles calculations to investigate the initial stages of titanium nanoparticle oxidation. We determine the most stable structure of a 181-atom decahedral nanoparticle with various oxygen coverages ranging from a single atom to full oxidation of the surface. Linear Oad–Ti–Oad bonding configurations on the nanoparticle surface are found to be most stable for low oxygen coverage. The degree of lattice expansion is observed to gradually increase with increasing oxygen content up to 8.2% for full oxidation of the surface. To investigate likely mechanisms for subsequent subsurface oxidation, we calculate energy barriers for many inequivalent oxygen diffusion pathways. We find that the most favorable pathways involve penetration of oxygen into subsurface octahedral sites in the center of facets where the strain is largest. The results provide atomistic insight into the oxidation behavior of Ti nanoparticles and highlight the important role played by adsorption induced strain.
Highlights
IntroductionThe understanding of how metallic nanoparticles oxidize is an important problem, since in many applications, they are exposed to an oxygen-rich environment (such as an ambient atmosphere, water, or an oxide substrate).[1−3] There are differences between nanoparticle oxidation and the oxidation of bulk surfaces, which are of fundamental interest
The understanding of how metallic nanoparticles oxidize is an important problem, since in many applications, they are exposed to an oxygen-rich environment.[1−3] There are differences between nanoparticle oxidation and the oxidation of bulk surfaces, which are of fundamental interest
Oxidized Ti nanoparticles find important applications in photocatalysis, e.g., in self-cleaning glass and water splitting.[8−10] We show that adsorbed oxygen atoms preferentially form linear Oad−Ti−Oad bonding configurations that involve two oxygen atoms bonded to one surface Ti atom
Summary
The understanding of how metallic nanoparticles oxidize is an important problem, since in many applications, they are exposed to an oxygen-rich environment (such as an ambient atmosphere, water, or an oxide substrate).[1−3] There are differences between nanoparticle oxidation and the oxidation of bulk surfaces, which are of fundamental interest. Oxygen atoms preferentially diffuse into the Ti nanoparticle in the center of facets where the dilative strain is largest. This investigation enhances the understanding of the oxidation of metallic nanoparticles and offers atomic insight into the interaction between oxygen atoms and the Ti nanoparticle surface. Guided ion beam mass spectrometry and photoelectron spectroscopy have shown that the morphology of Ti nanoparticles is icosahedral for N ≤ 130 (where N is the number of atoms in the nanoparticle).[11,12] The structure and stability of small Ti nanoparticles in several morphologies have been modeled using first-principles approaches with predictions in good agreement with experimental results.[13−15] As the size of nanoparticles increases, a transition to decahedral morphology is expected, which has a lower strain than icosahedral morphology.[16,17] Decahedral nanoparticles have 5-fold symmetry and expose 10 triangular close-packed facets.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.