Early Stages of Ti–O Cluster Growth on Carbon Nanotubes by ab Initio Calculations

Abstract

Ti-O combined with carbon nanotubes are excelled candidates for many technological applications. The early stages of growth comprise octahedral (Oh) anatase or rutile nanoparticles depending on the tetrahedral (Th) precursors. However, the underline mechanisms are still unknown. Here, we present results of a systematic study of Th or Oh clusters on (4,0) and (8,0). We found that although the Th may exist in several conformations, with well localized electronic states, the Oh is unstable. We found that due to charge localization and the emergence of C dangling bonds at the Fermi level, Th could be considered as more active compared to Oh that adopts the tube's C(2p)-C(2p) π-like features. In addition, when parallel to the tubes and along the zigzag chiral direction, the linear rutile-like trimers on zigzag (8,0), armchair (5,5), and (3,0)@(12,0) multiwall were clearly found to be energetically favored, while when vertically aligned, equi-probable rutile or spinal anatase-like growth is expected. At the Fermi level, the charge is localized at the Ti-O trimer, when on (5,5) and (3,0)@(12,0) cases, rendering Ti-O active. These results could enlighten the early stages of Ti-O growth on SWCNT providing useful information in the field of nanoelectronics and nanotechnology.

Insights into Reinforced Photocatalytic Activity of the CNT–TiO2 Nanocomposite for CO2 Reduction and Water Splitting

“…Only a few works related to the CNT–TiO 2 composite demonstrated methane, ethylene, and CO formation upon photoreduction of CO 2 , but all have the lower rate of product formation. ,, On the other hand, CNT–TiO 2 nanocomposites and their modifications with metals, such as Pt and Ni, for water splitting to produce hydrogen under UV and visible light have been reported. However, most of the reported studies require an excess amount of sacrificial electron donors such as alcohols, organic acids, and sulfide/sulfide, which make the process costly and impractical. − Combinations of TiO 2 and CNT have been studied computationally in many works. − However, intimate details of CNT–TiO 2 interactions and mechanism of photocatalytic action remained elusive. It is of great importance to develop more efficient nanocomposites of TiO 2 with CNT for a higher rate of CO 2 reduction and water splitting (without a sacrificial agent) as well as to have a profound insight into the interaction between TiO 2 and CNT.…”