Directly Anodized Sulfur-Doped TiO2 Nanotubes as Improved Anodes for Li-ion Batteries

TiO2 represents one of the promising anode materials for lithium ion batteries due to its high thermal and chemical stability, relatively high theoretical specific capacity and low cost. However, the electrochemical performance, particularly for mesoporous TiO2, is limited and must be further developed. Elemental doping is a viable route to enhance rate capability and discharge capacity of TiO2 anodes in Li-ion batteries. Usually, elemental doping requires elevated temperatures, which represents a challenge, particularly for sulfur as a dopant. In this work, S-doped TiO2 nanotubes were successfully synthesized in situ during the electrochemical anodization of a titanium substrate at room temperature. The electrochemical anodization bath represented an ethylene glycol-based solution containing NH4F along with Na2S2O5 as the sulfur source. The S-doped TiO2 anodes demonstrated a higher areal discharge capacity of 95 µAh·cm−2 at a current rate of 100 µA·cm−2 after 100 cycles, as compared to the pure TiO2 nanotubes (60 µAh·cm−2). S-TiO2 also exhibited a significantly improved rate capability up to 2500 µA·cm−2 as compared to undoped TiO2. The improved electrochemical performance, as compared to pure TiO2 nanotubes, is attributed to a lower impedance in S-doped TiO2 nanotubes (STNTs). Thus, the direct S-doping during the anodization process is a promising and cost-effective route towards improved TiO2 anodes for Li-ion batteries.

Zr4+-Doped Anatase TiO2 Nanotube Array Electrode for Electrocatalytic Reduction of L-cystine

A Zr⁴⁺-doped anatase TiO₂ nanotube array electrode was prepared using a process that included Ti anodizing, chemical immersion, and heat treatment. The compositions, microstructure, and electrochemical properties of the prepared electrodes were characterized. The results show that Zr⁴⁺ was successfully introduced into the TiO₂ nanotube array electrodes. Because Zr⁴⁺ was doped into the crystal structure of the TiO₂and replaced a part of Ti⁴⁺ to form more oxygen vacancies and Ti³⁺, the electrocatalytic activity of the prepared electrodes, for the reduction of L-cystine, was significantly improved.

Crystallization of TiO2-MoS2 Hybrid Material under Hydrothermal Treatment and Its Electrochemical Performance

Hydrothermal crystallization was used to synthesize an advanced hybrid system containing titania and molybdenum disulfide (with a TiO₂:MoS₂ molar ratio of 1:1). The way in which the conditions of hydrothermal treatment (180 and 200 °C) and thermal treatment (500 °C) affect the physicochemical properties of the products was determined. A physicochemical analysis of the fabricated materials included the determination of the microstructure and morphology (scanning and transmission electron microscopy—SEM and TEM), crystalline structure (X-ray diffraction method—XRD), chemical surface composition (energy dispersive X-ray spectroscopy—EDS) and parameters of the porous structure (low-temperature N₂ sorption), as well as the chemical surface concentration (X-ray photoelectron spectroscop—XPS). It is well known that lithium-ion batteries (LIBs) represent a renewable energy source and a type of energy storage device. The increased demand for energy means that new materials with higher energy and power densities continue to be the subject of investigation. The objective of this research was to obtain a new electrode (anode) component characterized by high work efficiency and good electrochemical properties. The synthesized TiO₂-MoS₂ material exhibited much better electrochemical stability than pure MoS₂ (commercial), but with a specific capacity ca. 630 mAh/g at a current density of 100 mA/g.

Osteotropic Radiolabeled Nanophotosensitizer for Imaging and Treating Multiple Myeloma

Rapid liver and spleen opsonization of systemically administered nanoparticles (NPs) for in vivo applications remains the Achilles' heel of nanomedicine, allowing only a small fraction of the materials to reach the intended target tissue. Although focusing on diseases that reside in the natural disposal organs for nanoparticles is a viable option, it limits the plurality of lesions that could benefit from nanomedical interventions. Here we designed a theranostic nanoplatform consisting of reactive oxygen (ROS)-generating titanium dioxide (TiO2) NPs, coated with a tumor-targeting agent, transferrin (Tf), and radiolabeled with a radionuclide (89Zr) for targeting bone marrow, imaging the distribution of the NPs, and stimulating ROS generation for cell killing. Radiolabeling of TiO2 NPs with 89Zr afforded thermodynamically and kinetically stable chelate-free 89Zr-TiO2-Tf NPs without altering the NP morphology. Treatment of multiple myeloma (MM) cells, a disease of plasma cells originating in the bone marrow, with 89Zr-TiO2-Tf generated cytotoxic ROS to induce cancer cell killing via the apoptosis pathway. Positron emission tomography/X-ray computed tomography (PET/CT) imaging and tissue biodistribution studies revealed that in vivo administration of 89Zr-TiO2-Tf in mice leveraged the osteotropic effect of 89Zr to selectively localize about 70% of the injected radioactivity in mouse bone tissue. A combination of small-animal PET/CT imaging of NP distribution and bioluminescence imaging of cancer progression showed that a single-dose 89Zr-TiO2-Tf treatment in a disseminated MM mouse model completely inhibited cancer growth at euthanasia of untreated mice and at least doubled the survival of treated mice. Treatment of the mice with cold Zr-TiO2-Tf, 89Zr-oxalate, or 89Zr-Tf had no therapeutic benefit compared to untreated controls. This study reveals an effective radionuclide sensitizing nanophototherapy paradigm for the treatment of MM and possibly other bone-associated malignancies.

Electrospun Nb2O5 nanorods/microporous multichannel carbon nanofiber film anode for Na+ ion capacitors with good performance

For the disadvantages of both the slow reaction kinetics and the poor conductivity for Nb₂O₅ electrode materials as sodium-ion capacitors (SICs), Nb₂O₅ NRs/NMMCNF film electrode with good flexibility and high electrochemical property has been fabricated by electrospinning PAN/PMMA/H₂Nb₂O₆·H₂O homogeneous viscous suspension and followed by an annealing treatment, in which the precursor H₂Nb₂O₆·H₂O nanorods are obtained by grinding H₂Nb₂O₆·H₂O nanowires, and Nb₂O₅ nanorods are uniformly embedded in nitrogen doped microporous multichannel carbon nanofiber. Benefiting from the multichannel network structure, Nb₂O₅ NRs/NMMCNF film electrode delivers the fast kinetics of Na⁺-storage and the superior Na-ion storage performance, it delivers outstanding rate capability (101 mAh g^-1 at 4 A g^-1) and ultralong lifespan (91% capacity retention after 10,000 cycles at 2 A g^-1). A Nb₂O₅ NRs/NMMCNF//AC SIC based on the Nb₂O₅ NRs@NMMCNF fiber film anode and the AC cathode is assembled. The energy density of the as-assembled device is as high as 91 Wh kg^-1 and its maximum power density is 7499 W kg^-1. This work offers a new structure design strategy toward intercalation-type metal oxide electrodes for application in SICs.

High-Capacity Interstitial Mn-Incorporated MnxFe3-xO4/Graphene Nanocomposite for Sodium-Ion Battery Anodes

Sodium-ion batteries (SIBs) have attracted wide attention because of their prospects for grid-scale electrical regulation and cost effectiveness of sodium. In this regard, iron oxides (FeO_x) are considered as one of the most promising anode candidates due to their high theoretical capacity and low cost. Unfortunately, the utilization of FeO_x anodes suffers from sluggish reaction kinetics and significant lattice variation, causing insufficient rate performance and fast capacity degradation during the sodiation/desodiation process. In this study, Mn ions are incorporated through interstitial sites into a Fe₃O₄ lattice to form the Mn-incorporated Fe₃O₄/graphene (M-Fe₃O₄/G) composites through a facile hydrothermal method. Confirmed by XRD Rietveld refinement and the first-principles calculation, Mn occupation into the body structure can effectively condense the electron density around the Fermi level and thus contributes to the increased electrical conductivity and improved electrochemical properties. Accordingly, the M_0.1Fe_2.9O₄/G composite demonstrates a high reversible capacity of 439.8 mA h g^-1 at a current density of 100 mA g^-1 over 200 cycles. Even at a high current density of 1 A g^-1, the M-Fe₃O₄/G composites remain stable for over 1200 cycles, delivering a capacity of 210 mA h g^-1. Coupled with a Na₃V₂(PO₄)₃-type cathode, the Mn-incorporated Fe₃O₄/G composites demonstrate good suitability in full SIBs (161.2 mA h g^-1 at the current density of 1 A g^-1 after 100 cycles). The regulation of Mn ions in the Fe₃O₄ lattice provides insights into the optimization of metal oxide anode candidates for their application in SIBs.

Pseudocapacitive Li-ion storage boosts high-capacity and long-life performance in multi-layer CoFe2O4/rGO/C composite

Due to the intrinsic low electrical conductivity and large volume expansion of the CoFe₂O₄ based active materials, designing more novel structures is still one of the most important challenges for its lithium ion battery application. In this work, the CoFe₂O₄/reduced graphene oxide/carbon (CFO/rGO/C) composite with integrated multi-layer structure has been synthesized through a facial two-step hydrothermal method. Benefiting from the introduction of the graphene network and amorphous carbon coating layer, as well as the accompanying synergistic effect, this composite can exhibit fast and reversible lithium intercalation/deintercalation reactions. With the aid of a surface-induced capacitive process, the CFO/rGO/C composite delivers a superior specific capacity (945 mA h g^-1 at 0.1 A g^-1) and excellent long-term cyclic stability (421 mA h g^-1 at 4 A g^-1 with closely 100% Coulombic efficiency after 2000 cycles). Significantly, at a high current density of 1 A g^-1, the reversible capacity exhibits a rapid increasing after 100 cycles and finally shows an ultra-high-capacity of 1430 mA h g^-1 over 500 cycles. This method could be generalized to the preparation of other similar transition metal oxide-based materials for the development of high-performance energy storage systems.

Copper ferrites@reduced graphene oxide anode materials for advanced lithium storage applications

Copper ferrites are emerging transition metal oxides that have potential applications in energy storage devices. However, it still lacks in-depth designing of copper ferrites based anode architectures with enhanced electroactivity for lithium-ion batteries. Here, we report a facile synthesis technology of copper ferrites anchored on reduced graphene oxide (CuFeO₂@rGO and Cu/CuFe₂O₄@rGO) as the high-performance electrodes. In the resulting configuration, reduced graphene offers continuous conductive channels for electron/ion transfer and high specific surface area to accommodate the volume expansion of copper ferrites. Consequently, the sheet-on-sheet CuFeO₂@rGO electrode exhibits a high reversible capacity (587 mAh g⁻¹ after 100 cycles at 200 mA g⁻¹). In particular, Cu/CuFe₂O₄@rGO hybrid, which combines the advantages of nano-copper and reduced graphene, manifests a significant enhancement in lithium storage properties. It reveals superior rate capability (723 mAh g⁻¹ at 800 mA g⁻¹; 560 mAh g⁻¹ at 3200 mA g⁻¹) and robust cycling capability (1102 mAh g⁻¹ after 250 cycles at 800 mA g⁻¹). This unique structure design provides a strategy for the development of multivalent metal oxides in lithium storage device applications.

K-ion and Na-ion storage performances of Co3O4-Fe2O3 nanoparticle-decorated super P carbon black prepared by a ball milling process

The hybridisation of Co₃O₄ and Fe₂O₃ nanoparticles dispersed in a super P carbon matrix is proposed as a favourable approach to improve the electrochemical performance (reversible capacity, cycling stability and rate capability) of the metal oxide electrodes in metal-ion batteries. Hybrid Co₃O₄-Fe₂O₃/C is prepared by a simple, cheap and easily scalable molten salt method combined with ball-milling and used in sodium-ion and potassium-ion batteries for the first time. The electrode exhibits excellent cycling stability and superior rate capability in sodium-ion cells with a capacity recovery of 440 mA h g^-1 (93% retention) after 180 long-term cycles at 50-1000 mA g^-1 and back to 50 mA g^-1. In contrast, Co₃O₄-Fe₂O₃, Co₃O₄ and Fe₂O₃ electrodes display unsatisfactory electrochemical performance. The hybrid Co₃O₄-Fe₂O₃/C is also reactive with potassium and capable of delivering a reversible capacity of 220 mA h g^-1 at 50 mA g^-1 which is comparable with the most reported anode materials for potassium-ion batteries. The obtained results broaden the range of transition metal oxide-based hybrids as potential anodes for K-ion and Na-ion batteries, and suggest that further studies of these materials with potassium and sodium are worthwhile.

Microwave-solvothermal synthesis of various TiO2 nano-morphologies with enhanced efficiency by incorporating Ni nanoparticles in an electrolyte for dye-sensitized solar cells

A novel systematic approach is demonstrated to enhance the efficiency of dye-sensitized solar cells by impregnating Ni-nanoparticles into I⁻/I₃⁻ electrolyte with various TiO₂ nanomorphologies-based photo-anodes synthesized via microwave-solvothermal process.

A simple spray reaction synthesis and characterization of hierarchically porous SnO2 microspheres for an enhanced dye sensitized solar cell

Hierarchical SnO₂ porous microspheres were synthesized by using a novel spray reaction technique. The efficiency of the SnO₂ microspheres-based DSSCs reaches 6.0%.

Electrospinning of Nanofibers for Energy Applications

With global concerns about the shortage of fossil fuels and environmental issues, the development of efficient and clean energy storage devices has been drastically accelerated. Nanofibers are used widely for energy storage devices due to their high surface areas and porosities. Electrospinning is a versatile and efficient fabrication method for nanofibers. In this review, we mainly focus on the application of electrospun nanofibers on energy storage, such as lithium batteries, fuel cells, dye-sensitized solar cells and supercapacitors. The structure and properties of nanofibers are also summarized systematically. The special morphology of nanofibers prepared by electrospinning is significant to the functional materials for energy storage.

Highly Ordered TiO2 Microcones with High Rate Performance for Enhanced Lithium-Ion Storage

The perpendicularly oriented anatase TiO2 microcones for Li-ion battery application were synthesized via anodization of a Ti foil in aqueous HF + H3PO4 solution. The TiO2 microcones exhibited a high active surface area with a hollow core depending on applied voltage and reaction time, confirmed by SEM, XRD and TEM with EDS mapping. Li insertion/desertion into TiO2 microcones was evaluated for the first time in half-cell configuration in terms of various current density and long-term cyclability. The electrochemical experiments demonstrated that the as-prepared TiO2 microcones as anode material exhibited 3 times higher capacity as compared with TiO2 nanotubular structures, excellent rate performance (0.054 mAhcm(-2) even at 50 C) and reliable capacity retention during 500 cycles, which was attributed to facile diffusion of Li-ions induced in hollow anatase TiO2 microcones structure with multilayered nanofragment.

Exfoliated Graphene Oxide/MoO2 Composites as Anode Materials in Lithium-Ion Batteries: An Insight into Intercalation of Li and Conversion Mechanism of MoO2

Exfoliated graphene oxide (EG)/MoO2 composites are synthesized by a simple solid-state graphenothermal reduction method. Graphene oxide (GO) is used as a reducing agent to reduce MoO3 and as a source for EG. The formation of different submicron sized morphologies such as spheres, rods, flowers, etc., of monoclinic MoO2 on EG surfaces is confirmed by complementary characterization techniques. As-synthesized EG/MoO2 composite with a higher weight percentage of EG performed excellently as an anode material in lithium-ion batteries. The galvanostatic cycling studies aided with postcycling cyclic voltammetry and galvanostatic intermittent titrations followed by ex situ structural studies clearly indicate that Li intercalation into MoO2 is transformed into conversion upon aging at low current densities while intercalation mechanism is preferably taking place at higher current rates. The intercalation mechanism is found to be promising for steady-state capacity throughout the cycling because of excess graphene and higher current density even in the operating voltage window of 0.005-3.0 V in which MoO2 undergoes conversion below 0.8 V.

3D interconnected hierarchically macro-mesoporous TiO2 networks optimized by biomolecular self-assembly for high performance lithium ion batteries

A 3D interconnected hierarchically macro-mesoporous TiO₂ network optimized by the mediation of biomolecular self-assembly has been used for high performance lithium storage.

Photo-active float for field water disinfection

Disinfection of field water contaminated with a wide array of bacteria (Gram negative and Gram positive) using a reusable photoactive float fabricated with visible light active nanostructured NFTiO₂.

Nano-Sn doped carbon-coated rutile TiO2 spheres as a high capacity anode for Li-ion battery

Nano-Sn doped carbon-coated rutile TiO₂ spheres (C-NS/TiO₂-1 and C-NS/TiO₂-2) as an improved TiO₂-based anode for Li-ion batteries were in situ fabricated.

Rapid flame synthesis of internal Mo(6+) doped TiO2 nanocrystals in situ decorated with highly dispersed MoO3 clusters for lithium ion storage

The rational design of nanoheterostructured materials has attracted much attention because of its importance for developing highly efficient LIBs. Herein, we have demonstrated that internal Mo(6+) doped TiO2 nanocrystals in situ decorated with highly dispersed MoO3 clusters have been realized by a facile and rapid flame spray pyrolysis route for electrochemical energy storage. In such intriguing nanostructures, internal Mo(6+) doping can improve the conductivity of electrode materials and facilitate rapid Li(+) intercalation and ion transport and the heteroassembly of highly dispersed ultrafine MoO3 clusters with excellent electrochemical activity endows the TiO2 with extra Li(+) ion storage ability as well as incorporates Mo(6+). Thus, the as-prepared nanohybrid electrodes exhibit a high specific capacity and superior rate capability due to the maximum synergetic effect of TiO2, Mo(6+) and ultrafine MoO3 clusters. Moreover, the aerosol flame process with a unique temperature gradient opens a new strategy to design novel hybrid materials by the simultaneous doping and heteroassembly engineering for next-generation LIBs.