Adsorption selectivity of TiCl4 precursor on Pt surfaces for atomic layer deposition via density functional theory

• Published in: Applied surface science 2022-12, Vol.606, p.154695, Article 154695
• Main Authors: Baek, Jihye, Nam, Kyungju, Park, Jung-yeon, Cha, JinHyeok
• Format: Article
• Language: English
• Subjects: Atomic layer deposition; Density functional theory; Precursors; Pt nanoparticles; Surface reaction; Titanium tetrachloride
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2022.154695

[Display omitted] •Implemented area-selective atomic layer deposition of TiCl4 precursors to surface fine control of Pt-based nanoparticle catalysts by DFT.•Investigated the surface characteristics of Pt nanoparticles by adsorption of OH groups and TiCl4 along the (100), (111), and (211) surfaces.•Analyzed the mechanism of the first half-cycle reaction via calculating the reaction activation energy between TiCl4 and the Pt-OH surface and the electronic structure.•Clarified that Pt (111) surface opens a favorable pathway for HCl release, and increases the surface reactivity. There is an interest in atomic layer deposition as a tool for precise catalyst design and synthesis, due to advantages such as uniform coating, excellent step coverage, and control of thin-film thickness at the atomic level. Using selective atomic layer deposition on platinum-based nanoparticle catalysts improves or maintains catalytic performance, and also improves sintering resistance under high-temperature and -pressure conditions through fine control of the surface. In this study, we used density functional theory to elucidate the mechanism of the initial TiCl4 half-cycle reaction for TiO2 formation on the surface of Pt nanoparticles, and the deposition characteristics according to the crystal properties. In the surface reaction, TiCl4 is adsorbed on Pt (111), (100), and (211) surfaces containing an –OH functional group, and the reaction proceeds through formation of a Pt−O−TiCl3 complex followed by HCl. The chemical adsorption of TiCl4 to the Pt−OH surface has an energy between −2.44 and −2.76 eV, thus providing a highly stable chemical bond. The activation energy of the TiCl4 half-cycle reaction on the surface of Pt nanoparticles is 1.15 – 1.24 eV, in the order Pt (211) > (100) > (111). Via electronic structure analysis of TiCl4-adsorbed Pt nanoparticles, we confirmed that the Pt (111) surface is a favorable pathway for the release of HCl, enhancing its response to the surface reaction. This study provides a quantitative understanding of the selective atomic layer deposition reaction of the precursor TiCl4 on Pt catalyst surfaces. As theoretical understanding of the deposition process improves, we expect that it will become possible to design precursor materials and process conditions applicable to the specifications required by various industries.