In‐Situ Carbon Doping of TiO₂ Nanotubes Via Anodization in Graphene Oxide Quantum Dot Containing Electrolyte and Carburization to TiO_xC_y Nanotubes

Abstract

Anodic production of self‐organized titania nanotubes (TNTs) in an electrolyte enriched with graphene oxide quantum dots (GOQDs) is reported. The TNT‐GOQD composites grown under these conditions show in‐situ carbon doping, leading to the formation of anatase TiO2 domains and to the reduction to substoichiometric oxide (TiOx) and TiC. Surface science and electrochemical techniques are used in synergy to reveal that graphitic carbon is incorporated into TiO2 upon anodic nanotube growth promoting the formation of oxygen vacancies and thus TiO2 reduction. Upon annealing in ultrahigh vacuum, titanium oxycarbide (TiOxCy) is formed at temperatures ≥400 °C, where the material changes from a semiconductor to a semimetal. At the solid/liquid interface, the apparent electron donor density increases from as‐grown TNTs to as‐grown TNT‐GOQD composites due to the carbon doping, and the conductivity increases further with annealing temperature due to the increasing concentration of coordinatively unsaturated C atoms, crystallinity, and TiO2 reduction. The materials synthesized and characterized in this study find application in different areas ranging from visible light photocatalysis and photo‐electrochemistry to use as Li‐ion battery anodes and electrocatalyst supports, because it is possible to gradually tune the density of states below the Fermi level, which can be referred to as band‐gap engineering.

Hierarchical MoS2 Nanosheet@TiO2 Nanotube Array Composites with Enhanced Photocatalytic and Photocurrent Performances

“…In order to address these obstacles, a plethora of strategies have been explored to improve the photoresponse of 1D TiO 2 NTAs. For example, metal/nonmetal impurity doping was shown to introduce mid‐gap energy levels, which were expected to control the band gap response of the TiO 2 NTAs and enhance their visible spectrum properties . In particular, the growth of TiO 2 ‐based composites (core‐shell geometry or nanoparticle decoration) is considered to be one of the most promising routes due to the improvement of charge carrier separation .…”

Nanogenerators Begin to Light Up: A Novel Poling‐Free Piezoelectric System with Multicolor Photoluminescence as an Efficient Mechatronics Development Platform

“…It can be seen clearly from the diagram that the spin‐coated PVDF/CQDs film irradiated different colors under variable excitation light sources, emitting blue light under the excitation of ultraviolet light, green light under blue, yellow light under green, and red light under the excitation of red light (Figure a–d). Thus, the PVDF/CQDs blend has the desirable essential multicolor fluorescent property before high‐pressure treatment, and this is because the luminescent effect is not only determined by the quantum size effect, but largely influenced by the surface defect and edge effect of the introduced CQDs . However, it is still vital to learn whether the as‐prepared compound still maintains this performance after a high‐pressure crystallization process, as this has direct influence on its application.…”

“…Compared with metal‐based QDs such as CdSe and CdTe and the raising concern over their environmental toxicity, biocompatibility, and stability, carbon quantum dots (CQDs), also called carbon nanodots, not only could avoid these problems by nature, but also exhibit unique and tunable photoluminescent and optical properties, nanoscale aqueous solubility, special physical and chemical properties, etc., thus leading to a bright future for their applications in environmental engineering, bioimaging as well as medical treatment . CQDs are structurally distinct from graphene quantum dots (GQDs) . The former are 3D quasi‐spherical nanoparticles usually <10 nm in diameter, and the later are 2D fragments of single or a few layered graphene, with lateral dimensions larger than their height …”

“…CQDs are structurally distinct from graphene quantum dots (GQDs) . The former are 3D quasi‐spherical nanoparticles usually <10 nm in diameter, and the later are 2D fragments of single or a few layered graphene, with lateral dimensions larger than their height …”

Electrochemically anodized one-dimensional semiconductors: a fruitful platform for solar energy conversion

“…Another efficient way to extend the photoresponse of anodized 1D semiconductors is non-metal element doping, most of which are mainly centered on carbon [120], nitrogen [121], sulfur [122], and phosphorus doping [123], which result in remarkably enhanced visible-light-driven photocatalytic performances. For example, tungsten trioxide (WO 3 ) prepared by anodization of W foil was doped with N via NH 4 OH treatment at high temperature (450°C) [124].…”