Capacitive and Charge Transfer Effects of Single‐Walled Carbon Nanotubes in TiO₂ Electrodes

Abstract

The transfer of nanoscale properties from single‐walled carbon nanotubes (SWCNTs) to macroscopic systems is a topic of intense research. In particular, inorganic composites of SWCNTs and metal oxide semiconductors are being investigated for applications in electronics, energy devices, photocatalysis, and electroanalysis. In this work, a commercial SWCNT material is separated into fractions containing different conformations. The liquid fractions show clear variations in their optical absorbance spectra, indicating differences in the metallic/semiconducting character and the diameter of the SWCNTs. Also, changes in the surface chemistry and the electrical resistance are evidenced in SWCNT solid films. The starting SWCNT sample and the fractions as well are used to prepare hybrid electrodes with titanium dioxide (SWCNT/TiO2). Raman spectroscopy reflects the optoelectronic properties of SWCNTs in the SWCNT/TiO2 electrodes, while the electrochemical behavior is studied by cyclic voltammetry. A selective development of charge transfer characteristics and double‐layer behavior is achieved through the suitable choice of SWCNT fractions.

Properties of Carbon Xerogels Supported Cobalt‐Based Catalysts and Their Performance in CO Hydrogenation Reaction

“…Carbon materials as support can overcome these drawbacks, they are usually chemical inert and no cobalt-support compounds are formed. [17,18] The potential applications of carbon nanomaterials such as carbon nanotubes (CNTs), carbon fibers, active carbon (AC) and graphene have attracted much attention [19,20] and significant progresses have been endeavored to overcome some issues including low aqueous solubility and high tendency to aggregate. However, the purity of CNTs and AC represents a lacuna of this kind of materials and several purification processes are required.…”

Charge-transfer characteristics in carbon nanostructure/metal oxide photoelectrodes efficiently probed by hydrogen peroxide

“…It has also been used as a complementary electron source to enhance the performance of photoanodes [7], which in turn, from a conceptual point of view, underlines its ability to accept photo-generated holes [8,9] On the other hand, carbon nanomaterials, including carbon nanotubes and graphene in their different varieties, may work as electron or hole acceptors when they form composites with photoactive semiconducting materials. Carbon nanotubes usually behave as electron acceptors and improve the photoactivity of TiO 2 at low nanotube contents [10]. For graphene, both electron [11] and hole acceptor [12,13]…”

“…The main characteristic of the SWCNT/TiO 2 electrode is the presence of large cathodic/anodic peaks in the TiO 2 bandgap region that can be associated to charge accumulation in the proximity of SWCNTs, due to the availability of new electronic states in the proximities of the TiO 2 conduction band[10]. In contrast, the rGO/TiO 2 voltammogram resembles the blank TiO 2 electrode.…”