Enhanced electrochemical performance of TiO2 by Ti3+ doping using a facile solvothermal method as anode materials for lithium-ion batteries

Titanium dioxide-based anode materials for lithium-ion batteries: structure and synthesis

Lithium-ion batteries (LIBs) have high energy density, long life, good safety, and environmental friendliness, and have been widely used in large-scale energy storage and mobile electronic devices. As a cheap and non-toxic anode material for LIBs, titanium dioxide (TiO₂) has a good application prospect. However, its poor electrical conductivity leads to unsatisfactory electrochemical performance, which limits its large-scale application. In this review, the structure of three TiO₂ polymorphs which are widely investigated are briefly described, then the preparation and electrochemical performance of TiO₂ with different morphologies, such as nanoparticles, nanowires, nanotubes, and nanospheres, and the related research on the TiO₂ composite materials with carbon, silicon, and metal materials are discussed. Finally, the development trend of TiO₂-based anode materials for LIBs has been briefly prospected.

Photocatalysis of TiO2 Sensitized with Graphitic Carbon Nitride and Electrodeposited Aryl Diazonium on Screen-Printed Electrodes to Detect Prostate Specific Antigen under Visible Light

We report on a photoelectrochemical (PEC) device to detect prostatic-specific antigen (PSA) under visible LED light irradiation within the point-of-care (POC) paradigm. The device consists of a 3D printed miniaturized photoelectrochemical system and a disposable PEC immunosensor made with screen-printed carbon electrodes (SPCEs). The SPCEs were coated with nickel single atoms anchored on graphitic carbon nitride (Ni-gC₃N₄), titanium dioxide nanoparticles (TiO₂), and aryl diazonium salt prepared from p-aminobenzoic acid. The electrodeposited aryl diazonium on Ni-gC₃N₄/TiO₂ decreased the recombination of photogenerated charge carriers, leading to a 3.1-fold increase in the photocurrent compared to pure TiO₂. This functionalization strategy provides carboxylic groups to anchor antibodies via the carbodiimide reaction, which may be extended to any other type of immunosensor. Under optimal conditions, the PEC immunosensor was able to detect PSA from 10^-16 to 10^-8 g mL^-1 with a detection limit of 0.06 fg mL^-1. The device robustness was confirmed with reproducibility and stability tests. PSA could also be detected in human serum samples, which demonstrates the potential of the PEC immunosensor for clinical diagnosis.

S-Doped Carbon Fibers Uniformly Embedded with Ultrasmall TiO2 for Na+ /Li+ Storage with High Capacity and Long-Time Stability

Building a rechargeable battery with high capacity, high energy density, and long lifetime contributes to the development of novel energy storage devices in the future. Although carbon materials are very attractive anode materials for lithium-ion batteries (LIBs), they present several deficiencies when used in sodium-ion batteries (SIBs). The choice of an appropriate structural design and heteroatom doping are critical steps to improve the capacity and stability. Here, carbon-based nanofibers are produced by sulfur doping and via the introduction of ultrasmall TiO₂ nanoparticles into the carbon fibers (CNF-S@TiO₂ ). It is discovered that the introduction of TiO₂ into carbon nanofibers can significantly improve the specific surface area and microporous volume for carbon materials. The TiO₂ content is controlled to obtain CNF-S@TiO₂ -5 to use as the anode material for SIBs/LIBs with enhanced electrochemical performance in Na⁺ /Li⁺ storage. During the charge/discharge process, the S-doping and the incorporation of TiO₂ nanoparticles into carbon fibers promote the insertion/extraction of the ions and enhance the capacity and cycle life. The capacity of CNF-S@TiO₂ -5 can be maintained at ≈300 mAh g^-1 over 600 cycles at 2 A g^-1 in SIBs. Moreover, the capacity retention of such devices is 94%, showing high capacity and good stability.

Solid-Gas Phase Photo-Catalytic Behaviour of Rutile and TiOn (1 < n < 2) Sub-Oxide Phases for Self-Cleaning Applications

The solid-gas phase photo-catalytic activities of rutile TiO₂ and TiO_n (1 < n < 2) sub-oxide phases have been evaluated. Varying concentrations of Ti³⁺ defects were introduced into the rutile polymorph of titanium dioxide through carbo-thermal reduction at temperatures ranging from 350 °C to 1300 °C. The resulting sub-oxides formed were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, impedance spectroscopy and UV-visible diffuse reflectance spectroscopy. The presence of Ti³⁺ in rutile exposed to high reduction temperatures was confirmed by X-ray diffraction. In addition, a Ti³⁺-Ti⁴⁺ system was demonstrated to enhance the photo-catalytic properties of rutile for the degradation of the air pollutants NO₂ and CO₂ under UV irradiation of wavelengths (λ) 376–387 nm and 381–392 nm. The optimum reduction temperature for photo-catalytic activity was within the range 350–400 °C and attributed to improved charge-separation. The materials that were subject to carbo-thermal reduction at temperatures of 350 °C and 400 °C exhibited electrical conductivities over one hundred times higher compared to the non-reduced rutile. The results highlight that sub-oxide phases form an important alternative approach to doping with other elements to improve the photo-catalytic performance of TiO₂. Such materials are important for applications such as self-cleaning where particles can be incorporated into surface coatings.

The transformation of anatase TiO2 to TiSe2 to form TiO2–TiSe2 composites for Li+/Na+ storage with improved capacities

We discovered and explored the basic conditions for the conversion of TiO₂-A to TiSe₂ and tested its electrochemical performance.

Switchable Intrinsic Defect Chemistry of Titania for Catalytic Applications

The energy crisis is one of the most serious issue that we confront today. Among different strategies to gain access to reliable fuel, the production of hydrogen fuel through the water-splitting reaction has emerged as the most viable alternative. Specifically, the studies on defect-rich TiO2 materials have been proved that it can perform as an efficient catalyst for electrocatalytic and photocatalytic water-splitting reactions. In this invited review, we have included a general and critical discussion on the background of titanium sub-oxides structure, defect chemistries and the consequent disorder arising in defect-rich Titania and their applications towards water-splitting reactions. We have particularly emphasized the origin of the catalytic activity in Titania-based material and its effects on the structural, optical and electronic behavior. This review article also summarizes studies on challenging issues on defect-rich Titania and new possible directions for the development of an efficient catalyst with improved catalytic performance.

Superior High-Rate and Ultralong-Lifespan Na3V2(PO4)3@C Cathode by Enhancing the Conductivity Both in Bulk and on Surface

Na₃V₂(PO₄)₃ has shown great promise in next-generation cathode materials for sodium-ion batteries owning to its fast Na⁺ diffusion in the three-dimensional open NASICON framework and high theoretical energy density. However, Na₃V₂(PO₄)₃ suffers from undesirable rate performance and unstable cyclability arising from low electronic conductivity. Herein, we propose a facile approach for significantly enhancing the electrochemical properties of Na₃V₂(PO₄)₃ by Ti doping at V site and constructing nanoparticle@carbon core-shell nanostructure. This material design provides fast electron conduction network within the whole active particles because of the mixed valence Ti^4+/3+ in bulk and highly conductive carbon shell on the surface. Lattice doping and carbon coating reduce the electrode polarization and facilitate the electrode reaction kinetics, while the nanostructure enhances the ionic conduction by shortening the diffusion distance and offers sufficient contact of active particles with organic electrolyte. The multiple synergetic effects enable a superior electrochemical performance. The optimized Na₃V_1.9Ti_0.1(PO₄)₃@C cathode shows a high specific capacity (116.6 mAh g^-1 at 1C), an unprecedented rate performance (93.4 mAh g^-1 at 400C), and an exceptional long-term high-rate cycling stability (capacity retention of 69.5% after 14 000 cycles at 100C, corresponding to 0.0002% decay per cycle).

High-performance lithium storage of Ti3+-doped anatase TiO2@C composite spheres

Ti³⁺-Doped anatase TiO₂@C composite spheres as the anode materials for lithium ion batteries.

The template-free synthesis of hierarchically porous anatase TiO2via acid-etching for enhancing the cycling stability and reversible capacity of lithium ion batteries

Two-dimensional hierarchically porous anatase TiO₂ is fabricated through acetic acid etching. It exhibit high electrochemical stability and high reversible capacity in lithium ion battery.

Highly photocatalytic TiO2 interconnected porous powder fabricated by sponge-templated atomic layer deposition

A titanium dioxide (TiO2) interconnected porous structure has been fabricated by means of atomic layer deposition of TiO2 onto a reticular sponge template. The obtained freestanding TiO2 with large surface area can be easily taken out of the water to solve a complex separation procedure. A compact and conformal nanocoating was evidenced by morphologic characterization. A phase transition, as well as production of oxygen vacancies with increasing annealing temperature, was detected by x-ray diffraction and x-ray photoelectron spectroscopy, respectively. The photocatalytic experimental results demonstrated that the powder with appropriate annealing treatment possessed excellent photocatalytic ability due to the co-action of high surface area, oxygen vacancies and the optimal crystal structure.