Room-Temperature Synthesis of Iron-Doped Anatase TiO2 for Lithium-Ion Batteries and Photocatalysis

Improved Lithium Storage Performance of a TiO2 Anode Material Doped by Co

TiO₂ is a promising anode material for lithium-ion batteries (LIBs) due to its low cost, suitable operating voltage, and excellent structural stability. The inherent poor electron conductivity and low ion diffusion coefficient, however, severely limit its application in lithium storage. Here, Co-doped TiO₂ is synthesized by a hydrothermal method as an anode material since Co@TiO₂ possesses a large specific surface area and high electronic conductivity. Thanks to the Co dopants, the ion diffusion and electron transport are both greatly improved, which is very beneficial for cycle stability, coulombic efficiency (CE), reversible capacity, and rate performance. As a result, Co@TiO₂ shows a high reversible capacity of 227 mAh g^-1 at 3 C, excellent rate performance, and cycling stability with a capacity of about 125 mAh g^-1 at 10C after 600 cycles (1 C = 170 mA g^-1).

Vertically Aligned Binder-Free TiO2 Nanotube Arrays Doped with Fe, S and Fe-S for Li-ion Batteries

Vertically aligned Fe, S, and Fe-S doped anatase TiO₂ nanotube arrays are prepared by an electrochemical anodization process using an organic electrolyte in which lactic acid is added as an additive. In the electrolyte, highly ordered TiO₂ nanotube layers with greater thickness of 12 μm, inner diameter of approx. 90 nm and outer diameter of approx. 170 nm are successfully obtained. Doping of Fe, S, and Fe-S via simple wet impregnation method substituted Ti and O sites with Fe and S, which leads to enhance the rate performance at high discharge C-rates. Discharge capacities of TiO₂ tubes increased from 0.13 mAh cm⁻²(bare) to 0.28 mAh cm⁻² for Fe-S doped TiO₂ at 0.5 C after 100 cycles with exceptional capacity retention of 85 % after 100 cycles. Owing to the enhancement of thermodynamic and kinetic properties by doping of Fe-S, Li-diffusion increased resulting in remarkable discharge capacities of 0.27 mAh cm⁻² and 0.16 mAh cm⁻² at 10 C, and 30 C, respectively.

Full-Process Radiosensitization Based on Nanoscale Metal-Organic Frameworks

Full-process radiosensitization, that is, pre-increasing radiation sensitivity of cancer cells, magnifying •OH formation during ionizing irradiation, and intervention on the resultant DNA repair for final cells death, could enhance the overall radiotherapeutic effects, but has not yet been achieved. Herein, Hf-nMOFs with Fe³⁺ ions uniformly dispersed (Hf-BPY-Fe) were constructed to integratedly improve radiotherapeutic effects via a multifaceted mechanism. The in vitro experiments demonstrated that persistent reactive oxygen species stress from Hf-BPY-Fe-activated in situ Fenton reaction reassorted cell cycle distribution, consequently contributing to increased tumoral radiosensitivity to photon radiation. Upon irradiation during the course of radiation therapy, Hf⁴⁺ in Hf-BPY-Fe gave substantial amounts of high-energy electrons, which partially converted H₂O to •OH and, meanwhile, relaxed to a low-energy state in nMOF pores, leading to an electron-rich environment. These aggregated electrons facilitated the reduction from Fe³⁺ to Fe²⁺ and further promoted the production of •OH in the Fenton process to attack DNA. The Hf-BPY-Fe postponed the DNA damage response process by interfering with certain proteins involved in the DNA repair signaling pathway. The in vivo experiments showed improved radiotherapeutic effects from integrated contributions from Fe³⁺-based Fenton reaction and Hf⁴⁺-induced X-ray energy conversion in tumors. This work provides a nMOFs-based full-process radiosensitizing approach for better radiotherapeutic efficacy.

Photocatalyzed Transformation of Free Carbohydrates

In the growing context of sustainable chemistry, one of the challenges of organic chemists is to develop efficient and environmentally friendly methods for the synthesis of high-added-value products. Heterogeneous photocatalytic transformations have brought revolution in this regard, as they take advantage of an unlimited source of energy (solar light) or artificial UV light to onset organic chemical modifications. The abundance of free carbohydrates as chemical platform feedstock offers a great opportunity to obtain a variety of industrial interest compounds from biomass. Due to their chirality and polyfunctionality, the conversion of sugars generally requires multi-step protocols with protection/deprotection steps and hazardous chemical needs. In this context, several selective and eco-friendly methodologies are currently under development. This review presents a state of art of the recent accomplishments concerning the use of photocatalysts for the transformation and valorization of free carbohydrates. It discusses the approaches leading to the selective oxidation of free sugars, their degradation into organic chemicals, or their use for hydrogen production.

Local vs Nonlocal States in FeTiO3 Probed with 1s2pRIXS: Implications for Photochemistry

Metal-metal charge transfer (MMCT) is expected to be the main mechanism that enables the harvesting of solar light by iron-titanium oxides for photocatalysis. We have studied FeTiO3 as a model compound for MMCT with 1s2pRIXS at the Fe K-edge. The high-energy resolution XANES enables distinguishing five pre-edge features. The three first well distinct RIXS features are assigned to electric quadrupole transitions to the localized Fe* 3d states, shifted to lower energy by the 1s core-hole. Crystal field multiplet calculations confirm the speciation of divalent iron. The contribution of electric dipole absorption due to local p-d mixing allowed by the trigonal distortion of the cation site is supported by DFT and CFM calculations. The two other nonlocal features are assigned to electric dipole transitions to excited Fe* 4p states mixed with the neighboring Ti 3d states. The comparison with DFT calculations demonstrates that MMCT in ilmenite is favored by the hybridization between the Fe 4p and delocalized Ti 3d orbitals via the O 2p orbitals.

Iron-Doped Cauliflower-Like Rutile TiO2 with Superior Sodium Storage Properties

Developing advanced anodes for sodium ion batteries is still challenging. In this work, Fe-doped three-dimensional (3D) cauliflower-like rutile TiO₂ was successfully synthesized by a facile hydrolysis method followed by a low-temperature annealing process. The influence of Fe content on the structure, morphology, and electrochemical performance was systematically investigated. When utilized as a sodium ion battery anode, 6.99%-Fe-doped TiO₂ exhibited the best electrochemical performance. This sample delivered a very high reversible capacity (327.1 mAh g^-1 at 16.8 mA g^-1) and superior rate performance (160.5 mAh g^-1 at 840 mA g^-1), as well as long-term cycling stability (no capacity fading at 1680 mA g^-1 over 3000 cycles). Density functional theory (DFT) calculations combined with experimental results indicated that the significantly improved sodium storage ability of the Fe-doped sample should be mainly due to the increased oxygen vacancies, narrowed band gap, and lowered sodiation energy barrier, which enabled much higher electronic/ionic conductivities and more favorable sodium ion intercalation into rutile TiO₂.

Green preparation of novel heptafluo-zirconate/hafnate nanocrystals at ambient temperature

A novel method to fabricate, under ambient conditions, pure and doped heptafluo-zirconate/hafnate nanocrystalsviaa convenient complex chemical procedure.

Synthesis and characterization of BiPO4/g-C3N4 nanocomposites with significantly enhanced visible-light photocatalytic activity for benzene degradation

BiPO₄/g-C₃N₄ nanocomposites were fabricated by a hydrothermal method including calcination and showed high photocatalytic activity under visible light.

Fe, S co-doped anatase TiO2 nanotubes as anodes with improved electrochemical performance for lithium ion batteries

Fe, S co-doped TiO₂ nanotubes are synthesized by a sol–gel and subsequent chemical process, exhibiting improved electrochemical performance for LIBs.

Direct Synthesis of Carbon-Doped TiO2-Bronze Nanowires as Anode Materials for High Performance Lithium-Ion Batteries

Carbon-doped TiO2-bronze nanowires were synthesized via a facile doping mechanism and were exploited as active material for Li-ion batteries. We demonstrate that both the wire geometry and the presence of carbon doping contribute to the high electrochemical performance of these materials. Direct carbon doping for example reduces the Li-ion diffusion length and improves the electrical conductivity of the wires, as demonstrated by cycling experiments, which evidenced remarkably higher capacities and superior rate capability over the undoped nanowires. The as-prepared carbon-doped nanowires, evaluated in lithium half-cells, exhibited lithium storage capacity of ∼306 mA h g(-1) (91% of the theoretical capacity) at the current rate of 0.1C as well as excellent discharge capacity of ∼160 mAh g(-1) even at the current rate of 10 C after 1000 charge/discharge cycles.

Phase stability frustration on ultra-nanosized anatase TiO2

This work sheds light on the exceptional robustness of anatase TiO2 when it is downsized to an extreme value of 4 nm. Since at this size the surface contribution to the volume becomes predominant, it turns out that the material becomes significantly resistant against particles coarsening with temperature, entailing a significant delay in the anatase to rutile phase transition, prolonging up to 1000 °C in air. A noticeable alteration of the phase stability diagram with lithium insertion is also experienced. Lithium insertion in such nanocrystalline anatase TiO2 converts into a complete solid solution until almost Li1TiO2, a composition at which the tetragonal to orthorhombic transition takes place without the formation of the emblematic and unwished rock salt Li1TiO2 phase. Consequently, excellent reversibility in the electrochemical process is experienced in the whole portion of lithium content.

Fe-doped anatase TiO2/carbon composite as an anode with superior reversible capacity for lithium storage

This paper reports an economic and effective wet chemistry process to prepare Fe-doped anatase TiO₂/carbon composite with excellent performance in lithium-ion batteries.