Oxygen Adsorption and Diffusion on NiTi Alloy (100) Surface: A Theoretical Study

Abstract

The formation of the passive oxide surface layer accounts for the superior biocompatibility of NiTi alloy based implant materials. However, the usage NiTi alloy is limited by the long-term release of biotoxic Ni ion from the bulk, facilitated by the formation of defects and vacancies in the surface oxide layer during conventional processing. To aid the improvement of the biocompatibility of NiTi alloys, extensive first-principles based calculations were performed to uncover the microscopic mechanism for the temperature controlled oxidation of NiTi alloy. We show that the oxygen adsorption and diffusion on the NiTi surface are the elementary steps for the formation of a surface oxide layer. Oxygen will bind strongly with the alloy surface and even induce surface reconstruction, and the adsorption energy can be as high as −6.14 eV. The requested surface diffusion for formation of TiO2 surface terminations is thermodynamics driven, but the corresponding kinetics is strongly affected by temperatures. These result in formation of TiO at low temperatures and TiO2 at elevated temperatures.

Pt atoms stabilized on hexagonal boron nitride as efficient single-atom catalysts for CO oxidation: a first-principles investigation

“…This phenomenon is widely observed in coverage dependent O adsorption on surfaces of transition metals and alloys. 64,65 We also considered the dissociation adsorption of O 2 , but found that the adsorption of 2 O atoms is less plausible as compared with that of O 2 by 0.38 eV and the barrier for O 2 dissociation is 0.92 eV. As the coadsorbed O or CO will further enlarge this barrier, the dissociative adsorption of O 2 less likely to take place.…”

Monodisperse Pt atoms anchored on N-doped graphene as efficient catalysts for CO oxidation: a first-principles investigation

“…dependent O adsorption on surfaces of transition metals and alloys. 71,72 We also analyzed the interaction between CO 2 and PtN3 and found that one of the π states of CO 2 interacts strongly with the Pt states and is downshifted to right below E F , showing the charge transfer from PtN3 to this state and the activation of the corresponding C-O bond.…”

CO oxidation catalyzed by Pt-embedded graphene: a first-principles investigation

“…This phenomenon is widely observed in coverage dependent O adsorption on surfaces of transition metals and alloys. 78,79 In the DOS plots, the peaks of O-sp states overlap with those of Pt-sp and Pt-d states around the E F , showing the strong hybridization among them. Comparing the peaks of adsorbed O 2 , the energy level of O-sp of adsorbed O atoms is higher and adjacent to the E F , which is a sign of the potential high oxidation activity.…”