High-performance supercapacitors based on amorphous C-modified anodic TiO2 nanotubes

One of the major challenges of implantology is to design nanoscale modifications of titanium implant surfaces inducing osseointegration. The aim of this study was to investigate the behavior of rat osteoblasts cultured on anodized TiO2 nanotubes of different crystallinity (amorphous and anatase phase) up to 24 days. TiO2 nanotubes were fabricated on VT1–0 titanium foil via a two-step anodization at 20 V using NH4F as an electrolyte. Anatase-phase samples were prepared by heat treatment at 500 °C for 1 h. VT1–0 samples with flat surfaces were used as controls. Primary rat osteoblasts were seeded over experimental surfaces for several incubation times. Scanning electron microscopy (SEM) was used to analyze tested surfaces and cell morphology. Cell adhesion and proliferation were investigated by cell counting. Osteogenic differentiation of cells was evaluated by qPCR of runt-related transcription factor 2 (RUNX2), osteopontin (OPN), integrin binding sialoprotein (IBSP), alkaline phosphatase (ALP) and osteocalcin (OCN). Cell adhesion and proliferation, cell morphology and the expression of osteogenic markers were affected by TiO2 nanotube layered substrates of amorphous and anatase crystallinity. In comparison with flat titanium, along with increased cell adhesion and cell growth a large portion of osteoblasts grown on the both nanostructured surfaces exhibited an osteocyte-like morphology as early as 48 h of culture. Moreover, the expression of all tested osteogenic markers in cells cultured on amorphous and anatase TiO2 nanotubes was upregulated at least at one of the analyzed time points. To summarize, we demonstrated that amorphous and anodized TiO2 layered substrates are highly biocompatible with rat osteoblasts and that the surface modification with about 1500 nm length nanotubes of 35 ± 4 (amorphous phase) and 41 ± 8 nm (anatase phase) in diameter is sufficient to induce their osteogenic differentiation. Such results are significant to the engineering of coating strategies for orthopedic implants aimed to establish a more efficient bone to implant contact and enhance bone repair.

Enhanced photocatalytic activity in TiO2 mixed phase nanostructures

Band alignment and charge transfer pathway in three phase anatase-rutile-brookite TiO2 nanotubes: An efficient photocatalyst for water splitting

The first-principles quantum mechanical investigation on CdS quantum dots (QDs) adsorbed on anatase TiO2 nanotubes (TiO2NTs) in quantum dot-sensitized solar cells (QDSSCs) was performed using the density functional theory (DFT) approach. The geometry and electronic coupling between a CdS QD and the TiO2NT have been examined for the first time, together with a detailed discussion of interfacial electron transfer and electron transport models along the TiO2NT. It has been found that adsorbate states are introduced in the band gap of the TiO2NT upon the adsorption of a CdS QD on the TiO2NT surface, and an electron transfers from the sulfur atoms of a CdS QD to the conduction band of the TiO2NT upon adsorption of visible light. The unique TiO2NT structure offers a one-dimensional directional pathway for electron transport across the semiconductor substrate through titanium dx2–y2 and dz2 orbitals. Our work is of great benefit for understanding the charge separation process at the heterogeneous interface and the key factors to govern the electron transport efficiency in TiO2NTs.

A vertically aligned anatase TiO2 (A-TiO2) nanotube array has been fabricated by coating a ZnO nanorod (NR) template with a TiO2 precursor solution. After coating, the ZnO NR cores were selectively etched in an acidic environment to form TiO2 nanotubes (NTs). More specifically, after growing the ZnO NRs via a hydrothermal method, one drop of the TiO2 precursor solution was cast to coat the ZnO NRs, the tops of which were previously covered with chemical capping materials by electrostatic interaction, and then the sample was sintered. Finally, the sample was immersed in an acidic solution resulting in selective etching of the ZnO NR cores. Thus, only TiO2 NTs remained on the substrate. The capping material is effectively used to create a perfect, hexagonal open-ended TiO2 NT array, which interestingly extends onset absorption towards the visible region.

Amorphous TiO2 nanotubes with diameters of 8-10 nm and length of several nanometers were synthesized by high pressure treatment of anatase TiO2 nanotubes. The structural phase transitions of anatase TiO2 nanotubes were investigated by using in-situ high-pressure synchrotron X-ray diffraction (XRD) method. The starting anatase structure is stable up to ∼20GPa, and transforms into a high-density amorphous (HDA) form at higher pressure. Pressure-modified high- to low-density transition was observed in the amorphous form upon decompression. The pressure-induced amorphization and polyamorphism are in good agreement with the previous results in ultrafine TiO2 nanoparticles and nanoribbons. The relationship between the LDA form and α-PbO2 phase was revealed by high-resolution transmission electron microscopy (HRTEM) study. In addition, the bulk modulus (B0 = 158 GPa) of the anatase TiO2 nanotubes is smaller than those of the corresponding bulks and nanoparticles (180-240 GPa). We suggest that the unique open-ended nanotube morphology and nanosize play important roles in the high pressure phase transition of TiO2 nanotubes.

The structural, electronic, and optical properties of metal (Si, Ge, Sn, and Pb) mono‐ and co‐doped anatase TiO2 nanotubes are investigated, to elucidate their potential for photocatalytic applications. It is found that Si‐doped TiO2 nanotubes are more stable than those doped with Ge, Sn, or Pb. All dopants lower the bandgap, except the (Ge, Sn) co‐doped structure, the decrease depending on the concentration and the type of dopant. Correspondingly, a redshift in the optical properties for all kinds of dopings is obtained. Even though a Pb mono‐ and co‐doped TiO2 nanotube has the lowest bandgap, these systems are not suitable for water splitting, due to the location of the conduction band edges, in contrast to Si, Ge, and Sn mono‐doped TiO2 nanotubes. On the other hand, co‐doping of TiO2 does not improve its photocatalytic properties. The findings are consistent with recent experiments, which show an enhancement of light absorption for Si‐ and Sn‐doped TiO2 nanotubes.

Carbon fiber electrodes were prepared by grafting anthraquinone molecules via a scalable electrochemical approach which simultaneously increased interfacial and electrochemical capacitance properties. In this work, anthraquinone diazonium salts were synthesized and grafted onto carbon fiber tows at various concentrations. These modified fibers were subsequently evaluated mechanically and electrochemically to analyze their suitability in structural supercapacitors. Compared to control fibers, the grafted anthraquinone groups resulted in a 30% increase in interfacial shear strength (IFSS) and 6.6× increase in specific capacitance. Industry application was also a focus thus carbon fibers were also modified with in-situ generated diazonium salts to determine the applicability to an in-line industrial process. Specifically, potentiostatic functionalization of fibers with in-situ generated diazonium salts AQ-1 and AQ-2, showed 3× and 4.3× increase in specific capacitance, respectively, relative to unmodified carbon fiber (CF). We expect that implementing a scalable method to introduce a conductive and electrochemically active covalently bound surface chemistry layer onto carbon fiber exhibits a higher specific capacitance than carbon fiber grafted with most other small molecules reported in literature. This will open new avenues for manufacturing multifunctional and high-performance fibers with tailored properties for specific/targeted applications.

Anatase TiO2 nanotubes synthesized via electrochemical anodization using a typical organic electrolyte are a promising candidate for photocatalytic H2 evolution. Despite the wide optical bandgap and low catalytic activity of TiO2, which impede its performance, our approach enhances photocatalytic properties through the introduction of platinum (Pt) single atoms (SAs) as a co-catalyst and simultaneously surface engineering by making defects, significantly enhancing its photocatalytic properties. This work shows photoanode TiO2 nanotubes (TiNT) have excellent harvesting properties for Pt SAs from a dilute hexachloroplatinic acid solution. Optimally annealed TiNTs provide surface Ti3+ suitable for anchoring SA species directly from the solution. The treated TiO2 nanotubes were characterized by field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photochemical hydrogen evolution. In the present study, we describe modifying the TiO2 nanotubes by loading Pt as a co-catalyst by simple immersion into dilute Pt solutions and defects by different intensities of high-power sonochemical treatment to enhance the photocatalytic hydrogen reaction rates. These findings show that ultrasound-treated TiNTs provide a remarkable substrate for SA decoration from dilute solutions aligned with promising performance, high H2 evolution catalysis, and renewable energy conversion, inspiring further research and potential applications in the field. Keywords: Anatase TiO2, Photocatalysis, H2 evolution, Co-catalyst References Hejazi, S., Mohajernia, S., Osuagwu, B., Zoppellaro, G., Andryskova, P., Tomanec, O., Kment, S., Zbořil, R., & Schmuki, P. (2020). On the Controlled Loading of Single Platinum Atoms as a Co-Catalyst on TiO2 Anatase for Optimized Photocatalytic H2 Advanced Materials, 32(16). https://doi.org/10.1002/adma.201908505Shahrezaei, M., Hejazi, S. M. H., Kmentova, H., Sedajova, V., Zboril, R., Naldoni, A., & Kment, S. (2023). Ultrasound-Driven Defect Engineering in TiO2-x Nanotubes─Toward Highly Efficient Platinum Single Atom-Enhanced Photocatalytic Water Splitting. ACS Applied Materials and Interfaces, 15(31), 37976–37985. https://doi.org/10.1021/acsami.3c04811Wu Z, Hwang I, Cha G, et al. Optimized Pt Single Atom Harvesting on TiO2 Nanotubes—Towards a Most Efficient Photocatalyst. Small. 2022;18(2). doi:10.1002/smll.20210489Shahsanaei, M., Farahbakhsh, N., Pour-Ali, S., Schardt, A., Orangpour, S., Engelhard, C., Mohajernia, S., Killian, M. S., & Hejazi, S. (2024). Synergistic enhancement of photocatalytic hydrogen production in TiO2 nanosheets through light-induced defect formation and Pt single atoms. Journal of Materials Chemistry A. https://doi.org/10.1039/d4ta01809e Figure 1

Plasma-induced synthesis of Pt nanoparticles supported on TiO2 nanotubes for enhanced methanol electro-oxidation

Preparation and physico-chemical investigation of anatase TiO2 nanotubes for a stable anode of lithium-ion battery

TiO2 nanotubes as alternative cathode in microbial fuel cells: Effect of annealing treatment on its performance

Polyaniline-decorated hyaluronic acid-carbon nanotube hybrid microfiber as a flexible supercapacitor electrode material

The photoelectrochemical performance of Ag coated CeO2 functionalized TiO2 nanotube arrays (AgCeTNT) is investigated here. The sample is prepared via three steps, such as synthesis of TiO2 nanotube by electrochemical anodization, CeO2 functionalization by hydrothermal and Ag coating by Successive Ionic Layer Adsorption and Reaction (SILAR) method. X-ray diffraction (XRD) analysis showed the anatase phase formation after annealing of TiO2 nanotubes. Field Emission Scanning Electron Microscopic (FESEM) images showed the conformal coverage of CeO2 and Ag nanoparticles on the surface of TiO2 nanotubes. Energy Dispersive X-Ray (EDX) analysis confirmed the presence of Ce, Ag, Ti and O in the AgCeTNT sample. Diffuse Reflectance Spectroscopy (DRS) study revealed the enhancement in visible light sensitivity with CeO2 functionalization and further with Ag coating. The photoelectrochemical measurement showed that the AgCeTNT sample exhibits improved photoelectrochemical performance compared to bare TiO2 nanotubes (TNT), CeO2 functionalized TiO2 nanotubes (CeTNT) and Ag coated TiO2 nanotubes (AgTNT) under the illumination of sunlight. This improvement in photoelectrochemical performance happeneddue to the combined effect of favorable band alignment of CeO2 and TiO2 and Surface Plasmon Resonance (SPR) effect of Ag nanoparticles, which lead to superior charge separation, efficient charge transport and enhanced visible light response.

Synthesis and characterization of anatase TiO2 nanotubes with controllable crystal size by a simple MWCNT template method