Ti-based Oxides Research Articles

New stable rare earth Ti-based semiconductor pyrochlore oxides for low-cost energy applications

New stable rare earth Ti-based semiconductor pyrochlore oxides for low-cost energy applications

Efficient Surface Passivation of Ti-Based Layered Materials by a Nonfluorine Branched Copolymer for Durable and High-Power Sodium-Ion Batteries.

There is a crucial need for low-cost energy storage technology based on abundant sodium ions to realize sustainable development with renewable energy resources. Poly(vinylidene fluoride) (PVDF) is applied as a binder in sodium-ion batteries (SIBs). Nevertheless, PVDF is also known to suffer from a larger irreversible capacity, especially when PVDF is used as the binder of negative electrode materials. In this research, a poly(acrylonitrile)-grafted poly(vinyl alcohol) copolymer (PVA-g-PAN) is tested as a binder with Ti-based layered oxides as potential negative electrode materials for SIBs. The chemical stability tests of PVDF and PVA-g-PAN contacted with metallic sodium have been conducted, which reveals that PVDF experiences a defluorination process, while PVA-g-PAN demonstrates excellent chemical stability. Composite electrodes with PVA-g-PAN demonstrate superior electrochemical performances when compared with the PVDF binder, allowing improvement for initial CE, higher rate capability, and long cyclability over 1500 cycles. Detailed characterization of electrodes via soft X-ray photoelectron spectroscopy and field emission scanning electron microscopy demonstrates that the PVA-g-PAN branched structure allows a more uniform distribution of acetylene black with higher coatability, unlocking enhanced rate performances and efficient passivation of Ti-based oxides without the excessive electrolyte decomposition. These findings open a new way to design practical and durable sodium-ion batteries with a high-power density.

Acid and base catalysis of SrTiO3 nanoparticles for C–C bond-forming reactions

The development of acid–base bifunctional catalysts is important because of their cooperative activation of a substrate to promote specific chemical transformations. We investigated two C–C bond-forming reactions—cyanosilylation and Knoevenagel condensation—over Ti-based perovskite oxides synthesized by a sol–gel method using water-soluble metal precursors and dl-malic acid. Among the tested catalysts, highly pure SrTiO3 nanoparticles (23 nm) with a high specific surface area (46 m2 g–1) exhibited the highest catalytic performance for the reactions, even when it was not subjected to a thermal pretreatment. The SrTiO3 catalyst could be easily recovered by simple filtration and reused two times without a substantial loss of its performance for the Knoevenagel condensation of benzaldehyde with phenylacetonitrile. Mechanistic studies—including studies of the effect of electron-withdrawing groups on the substrates, studies of the poisoning effect of acidic and basic additives for Knoevenagel condensation, and FT-IR measurements of probe molecules adsorbed onto the catalyst surface—revealed that acid and base sites on the catalyst surface cooperatively activate active methylene compounds with nitrile groups to promote the reactions effectively.

Recent Advances and Challenges in Ti-Based Oxide Anodes for Superior Potassium Storage.

Developing high-performance anodes is one of the most effective ways to improve the energy storage performances of potassium-ion batteries (PIBs). Among them, Ti-based oxides, including TiO2, K2Ti6O13, K2Ti4O9, K2Ti8O17, Li4Ti5O12, etc., as the intrinsic structural advantages, are of great interest for applications in PIBs. Despite numerous merits of Ti-based oxide anodes, such as fantastic chemical and thermal stability, a rich reserve of raw materials, non-toxic and environmentally friendly properties, etc., their poor electrical conductivity limits the energy storage applications in PIBs, which is the key challenge for these anodes. Although various modification projects are effectively used to improve their energy storage performances, there are still some related issues and problems that need to be addressed and solved. This review provides a comprehensive summary on the latest research progress of Ti-based oxide anodes for the application in PIBs. Besides the major impactful work and various performance improvement strategies, such as structural regulation, carbon modification, element doping, etc., some promising research directions, including effects of electrolytes and binders, MXene-derived TiO2-based anodes and application as a modifier, are outlined in this review. In addition, noteworthy research perspectives and future development challenges for Ti-based oxide anodes in PIBs are also proposed.

Effect of Ti-Based Additives on the Hydrogen Storage Properties of MgH2: A Review

For the few past decades, study of new hydrogen storage materials has been captivating scientists worldwide. Magnesium hydride, MgH2, is considered one of the most promising materials due to its low cost, high hydrogen capacity, reversibility and the abundance of Mg. However, it requires further research to improve its hydrogen storage performance as it has some drawbacks such as poor dehydrogenation kinetic, high operational temperature, which limit its practical application. In this study, we introduce an overview of recent progress in improving the hydrogen storage performance of MgH2 by the addition of titanium-based additives, which are one of the important groups of additives. The role of Ti-based additive hydrides, oxides, halides, carbides and carbonitrides are overviewed. In addition, the existing challenges and future perspectives of Mg-based hydrides are also discussed.

Internal Electric Field Built on Heterointerface of H2TiO3/H4Ti5O12 Hybrid Enabling Promoted Li Extraction Performance.

With potentially high lithium (Li) exchange capacity and long cycle ability, Ti-based oxides of H2TiO3 and H4Ti5O12 are considered to be promising Li-ion sieve (LIS) materials applied for Li resource extraction in the liquid phase. However, the LISs usually demonstrate unsatisfactory Li exchange performance under the approximately neutral condition without the strong impetus derived from the rapid combination between OH- in the surrounding solution and H+ ionized from LIS. Herein, a hybrid of H2TiO3/H4Ti5O12 with rich phase boundaries is constructed via a facile one-step solid-state method. Owing to the different Fermi energy levels of the two phases, the electrons are transferred at the phase interface between H2TiO3 and H4Ti5O12, developing an internal electric field (IEF). The built IEF provides an extra driving force to boost the solid-phase Li+ transport, hence enhancing the Li extraction kinetics. Threrfore, the H2TiO3/H4Ti5O12 hybrid exhibits outstanding Li exchange performance of 42.43 and 20.50 mg g-1 under alkaline and neutral conditions, corresponding to the hightest Li extraction rate of 5.30 and 2.05 mg g-1 h-1 reported so far. Our work offers an innovative strategy to promote the Li exchange performance of LIS especially under neutral conditions.

A Review on Nano Ti-Based Oxides for Dark and Photocatalysis: From Photoinduced Processes to Bioimplant Applications.

Catalysis on TiO2 nanomaterials in the presence of H2O and oxygen plays a crucial role in the advancement of many different fields, such as clean energy technologies, catalysis, disinfection, and bioimplants. Photocatalysis on TiO2 nanomaterials is well-established and has advanced in the last decades in terms of the understanding of its underlying principles and improvement of its efficiency. Meanwhile, the increasing complexity of modern scientific challenges in disinfection and bioimplants requires a profound mechanistic understanding of both residual and dark catalysis. Here, an overview of the progress made in TiO2 catalysis is given both in the presence and absence of light. It begins with the mechanisms involving reactive oxygen species (ROS) in TiO2 photocatalysis. This is followed by improvements in their photocatalytic efficiency due to their nanomorphology and states by enhancing charge separation and increasing light harvesting. A subsection on black TiO2 nanomaterials and their interesting properties and physics is also included. Progress in residual catalysis and dark catalysis on TiO2 are then presented. Safety, microbicidal effect, and studies on Ti-oxides for bioimplants are also presented. Finally, conclusions and future perspectives in light of disinfection and bioimplant application are given.

Recent Advances of Oxygen Carriers for Hydrogen Production via Chemical Looping Water-Splitting

Hydrogen is an important green energy source and chemical raw material for various industrial processes. At present, the major technique of hydrogen production is steam methane reforming (SMR), which suffers from high energy penalties and enormous CO2 emissions. As an alternative, chemical looping water-splitting (CLWS) technology represents an energy-efficient and environmentally friendly method for hydrogen production. The key to CLWS lies in the selection of suitable oxygen carriers (OCs) that hold outstanding sintering resistance, structural reversibility, and capability to release lattice oxygen and deoxygenate the steam for hydrogen generation. Described herein are the recent advances in designing OCs, including simple metal oxides (e.g., Fe, Zn, Ce, and Ti-based metal oxides) and composite metal oxides (e.g., perovskite, spinel, and garnets), for different CLWS processes with emphasis on the crucial parameters that determine their redox performance and future challenges.

Heterostructured MXene-derived oxides as superior photocatalysts for MB degradation

This work offers a simple and effective strategy to design a two-dimensional layer heterostructure of carbon/Ti-based oxide nanocomposites via a long-term oxidation process of MXene (Ti 3 C 2 T x ). Oxidation kinetics parameters concluded that MXene initially reacted with oxygen by forming the carbon layer and nanostructured Ti-based oxides with a homogeneous distribution, including TiOF 2 and TiO 2 , whereas the further oxidation process was governed by oxygen diffusion. It suggested that lower oxidation temperature and longer time (300 °C/1 h) facilitated to fabricate carbon-supported TiO 2 @TiOF 2 heterojunction nanocomposites with a unique 2D layer structure, which achieved a 90 % removal of methylene blue (MB) at 1 h under visible light illumination, owning to its large specific surface area, good electronic conductivity, narrowed band-gap, enhanced absorption in the visible range and high charge separation efficiency. Hence, the designed MXene-derived oxides were considered as promising candidates for wide-range responsive photocatalytic degradation of pollutants. ● Ti-based oxides with different architecture were constructed via isothermal oxidation treatment of MXene (Ti 3 C 2 T x ). ● Oxidation of Ti 3 C 2 T x was initially governed by the surface reaction, and then controlled by the oxygen diffusion process. ● Lower temperature and longer holding time was the optimal oxidation condition to construct 2D C/TiO 2 @TiOF 2 heterojunction.

First-principles study of oxygen vacancy formation in strained oxides

Based on first-principles density functional theory calculations and chemical bond analyses, we attempted to study the formation of oxygen vacancies (VO) in strained Ti-based oxides. Structural features (e.g., cell volume and mean Ti–O bond length) exhibit a clear and linear correlation with strain. Further, electronic features (e.g., bandgap and Ti–O covalent bond strength) exhibit similar trends for hydrostatic, biaxial, and uniaxial strains, except for shear strains. We investigated the impact of strain on the formation of VO and found that the formation energy in strained oxides was almost linearly linked to changes in the cell volume, bandgap, and Ti–O bond strength of the host oxide, where VO were formed. However, these correlations are not valid in compressively strained systems, which include Ti–O bonds—the bond length being shorter than the sum of Ti and O ionic radii, and shear-strained systems.

O3-Type Na2/3Ni1/3Ti2/3O2 Layered Oxide as a Stable and High-Rate Anode Material for Sodium Storage

Sodium-ion batteries (SIBs) are currently the most promising candidates for large-scale energy storage devices owing to their low cost and abundant resources. Titanium-based layered oxides have attracted widespread attention as promising anode materials due to delivering a safe potential of about 0.7 V (vs Na+/Na) and a small volume contraction during cycles; P2-type Ti-based layered oxides are typically reported, due to the challenging synthesis of the O3-type counterpart resulting from the high percentage of unstable Ti3+. Herein, we report an anomalous O3-Na2/3Ni1/3Ti2/3O2 layered oxide as an ultrastable and high-rate anode material for SIBs. The anode material delivers a reversible capacity of 112 mA h g-1 after 300 cycles at 0.1 C, a good capacity retention rate of 91% after 1400 cycles at 2 C, and, in particular, a capacity of 52 mA h g-1 even at a high rate of 20 C (1780 mA g-1). Furthermore, the in situ X-ray diffraction monitoring reveals no phase transitions and almost zero strain both underlie the good long-cycle stability. The measured high apparent Na+ diffusion coefficient (2.06 × 10-10 cm2 s-1) and the low migration energy barrier (0.59 eV) from density functional theory calculations are responsible for the superior rate capability. Our results promise advanced high-performance O3-type Ti-based layered oxides as promising anode materials toward application for SIBs.

Factors influencing phase formation and band gap studies of a novel multicomponent high entropy (Co,Cu,Mg,Ni,Zn)2TiO4 orthotitanate spinel

High entropy oxides (HEOs) with 5 or more cations in a single sublattice have recently emerged as a novel class of ceramic materials with interesting properties in the fields of energy and electronics. On the other hand, Ti-based oxides are well-known for their applications in the field of energy harvesting. In this study, Ti was added to a transition metal high entropy oxide, TM-HEO (Co,Cu,Mg,Ni,Zn)O and, a phase-pure orthotitanate inverse spinel structure (tetragonal lattice – P4122 space group) was obtained as (Co,Cu,Mg,Ni,Zn)2TiO4 and confirmed by X-ray diffraction (XRD) studies. The presence of tetragonal distortion was confirmed from Fourier transform infra-red (FTIR) spectroscopy and attributed to the smaller ionic radii of Ti. The degree of inversion in the spinel structure was studied by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The stoichiometry, distribution of cations and the defect states in the compound were also quantified from XPS. The effect of the individual cations in the phase formation was analysed through the systematic elimination of each cation from the (Co,Cu,Mg,Ni,Zn)2TiO4 system, which revealed that formation of a phase-pure spinel structure was achieved when a 1:2 ratio of cations occupying the tetrahedral to octahedral sites was maintained. The band gap energies of the (Co,Cu,Mg,Ni,Zn)2TiO4 system as well as those of the phase-pure lower combination spinels were found to be in the infrared range of 1.02–1.54 eV which varied with the composition and the fact that it was lower than any of the individual oxides could be attributed to the band alignment of the individual cations. Band diagram for (Co,Cu,Mg,Ni,Zn)2TiO4 was constructed from the valence band spectrum obtained from the XPS studies. (Co,Cu,Mg,Ni,Zn)2TiO4 could, therefore, be a potential material for light harvesting applications as the band gap lies in the infrared regime.

Mesoporous TiO2 from Metal-Organic Frameworks for Photoluminescence-Based Optical Sensing of Oxygen

Metal−organic frameworks (MOFs) are a class of porous coordination networks extraordinarily varied in physicochemical characteristics such as porosity, morphologies, and compositions. These peculiarities make MOFs widely exploited in a large array of applications, such as catalysis, chemicals and gas sensing, drug delivery, energy storage, and energy conversion. MOFs can also serve as nanostructured precursors of metal oxides with peculiar characteristics and controlled shapes. In this work, starting from MIL125-(Ti), a 1,4-benzenedicarboxylate (BDC)-based MOF with Ti as metallic center, mesoporous TiO2 powders containing both anatase and rutile crystalline phases were produced. A challenging utilization of these porous MOF-derived Ti-based oxides is the optically-based quantitative detection of molecular oxygen (O2) in gaseous and/or aqueous media. In this study, the photoluminescence (PL) intensity changes during O2 exposure of two MOF-derived mixed-phase TiO2 powders were probed by exploiting the opposite response of rutile and anatase in VIS-PL and NIR-PL wavelength intervals. This result highlights promising future possibilities for the realization of MOF-derived doubly-parametric TiO2-based optical sensors.

Rational design of Ti-based oxygen redox layered oxides for advanced sodium-ion batteries

Rational design of Ti-based layered oxides, enabling the utilization of oxygen redox for advanced sodium-ion batteries.

Synthesis of tetragonal BaTiO3 nano-particle via a novel tartaric acid co-precipitation process

A novel tartaric acid co-precipitation process was firstly reported to prepare tetragonal BaTiO3 nano-powder with barium chloride, titanium tetrachloride as raw materials and tartaric acid as precipitant agent. The as-obtained BaTiO3 powder exhibited a small average particle size about 140 nm, which still held a high tetragonality (c/a ratio) of 1.0092, suggesting its promising applications in multilayer ceramic capacitors (MLCC). In addition, this synthetic method will be of general interest to people who focuses on synthesis technology of Ti-based multicomponent oxides nano-materials owing to its outstanding advantages, including mild reaction condition, facile synthetic processes and especially stabilization of (TiO)2+ even in a high pH about 8.

Defect Engineering in Titanium-Based Oxides for Electrochemical Energy Storage Devices

Defect engineering involves the manipulation of the type, concentration, mobility or spatial distribution of defects within crystalline structures and can play a pivotal role in transition metal oxides in terms of optimizing electronic structure, conductivity, surface properties and mass ion transport behaviors. And of the various transition metal oxides, titanium-based oxides have been keenly investigated due to their extensive application in electrochemical storage devices in which the atomic-scale modification of titanium-based oxides involving defect engineering has become increasingly sophisticated in recent years through the manipulation of the type, concentration, spatial distribution and mobility of defects. As a result, this review will present recent advancements in defect-engineered titanium-based oxides, including defect formation mechanisms, fabrication strategies, characterization techniques, density functional theory calculations and applications in energy conversion and storage devices. In addition, this review will highlight trends and challenges to guide the future research into more efficient electrochemical storage devices. This work reviews the recent advances in defect-engineered Ti-based oxides, including the mechanism of defect formation, fabrication strategies, the characterization techniques, density functional theory calculations and the applications in energy conversion and storage.

Dehydration-triggered electronic structure modulation enables high-performance quasi-solid-state Li-ion capacitors

Ti-based oxides have attracted extensive attention as promising lithium-intercalated materials for hybrid capacitors. However, the low electronic conductivity and sluggish lithiation dynamics hinder their performance including reversible capacity, rate capability, and cycle stability. Herein, we report a kind of quasi-layered titanate hydrates (Q-TH) deriving from the dehydration-induced structural rearrangement of Ti-O octahedra and their superior electrochemical performance in the quasi-solid-state Li-ion capacitors. As predicted by Mulliken charge analysis, the surrounding O atoms will transfer electrons to the central Ti atoms accompanying with the detachment of bonding -OH groups. The resulting unpaired 3d electron would be injected into the t2g* antibonding orbital, deflecting the conduction band to the Fermi level and introducing intermediate bands within the bandgap, thereby enhancing the electronic conductivity of Q-TH. Such a special electronic structure will reduce polarization, facilitate fast Li-ion diffusion and lower the activation barrier (0.309 eV). Hence, impressive energy densities (116 Wh kg−1) and competitive cycling ability (86%, 3000 cycles) can be achieved when used as additive-free anodes in quasi-solid-state LICs with graphene nanosheets (GNS) cathodes. Thus, dehydration could be an effective way to modulate the electronic structure of titanate hydrates instead of just an approach to removing water.

Ti-Based Oxide Anode Materials for Advanced Electrochemical Energy Storage: Lithium/Sodium Ion Batteries and Hybrid Pseudocapacitors.

Titanium-based oxides including TiO2 and M-Ti-O compounds (M = Li, Nb, Na, etc.) family, exhibit advantageous structural dynamics (2D ion diffusion path, open and stable structure for ion accommodations) for practical applications in energy storage systems, such as lithium-ion batteries, sodium-ion batteries, and hybrid pseudocapacitors. Further, Ti-based oxides show high operating voltage relative to the deposition of alkali metal, ensuring full safety by avoiding the formation of lithium and sodium dendrites. On the other hand, high working potential prevents the decomposition of electrolyte, delivering excellent rate capability through the unique pseudocapacitive kinetics. Nevertheless, the intrinsic poor electrical conductivity and reaction dynamics limit further applications in energy storage devices. Recently, various work and in-depth understanding on the morphologies control, surface engineering, bulk-phase doping of Ti-based oxides, have been promoted to overcome these issues. Inspired by that, in this review, the authors summarize the fundamental issues, challenges and advances of Ti-based oxides in the applications of advanced electrochemical energy storage. Particularly, the authors focus on the progresses on the working mechanism and device applications from lithium-ion batteries to sodium-ion batteries, and then the hybrid pseudocapacitors. In addition, future perspectives for fundamental research and practical applications are discussed.

Thin Film Lithium Niobites with Intrinsic High-Rate Performance for Lithium-Ion Batteries

Lithium-ion batteries have been broadly favored as one of the best energy storage systems which have various classes of electrode materials being studied to satisfy the demand on improved electrochemical performance. As a similar class to titanium-based oxides, niobium-based oxides continue to be considered as promising electrode materials with multiple pairs of Nb redox couples, which can deliver more capacity than Ti-based oxides depending on their phase and charge/discharge condition. Among several phases of niobium oxides, lithium niobite (LiNbO2) has attracted scientific attention as a mixed ion-electron conductor proposing its use for the optical application as well as memristor and superconductor. Nevertheless, the research on lithium niobites still lacks, especially for the use as energy storage materials in lithium-ion batteries. By sputter deposition, 1.1-micron-thick lithium niobite membranes were fabricated for thin film electrodes. The characterization using XRD and XPS with consecutive etching confirmed the unique (101)-oriented crystalline arrangement of as-synthesized thin film electrodes and elucidated their initial lithium deficiency. Free of conducting agent and binder, the electrodes exhibited high capacity utilization and stable retention over 400 cycles. They also presented remarkable high-rate performance even at 14 A/g of extremely high current density (ca. 70C) and demonstrated a full recovery of capacity at the subsequent moderate rate. It was revealed the unit parameter change originated from the insertion and desertion of lithium cations occupying the octahedral sites between (NbO2)n- layers of edge-shared NbO6 trigonal prisms. None of phase evolution or extinction during the cycling implies that the major capacity contribution of lithium niobite comes from the single-phase intercalation reactions, which was supported by voltage profiles as well. Post-mortem analysis using XPS with Ar ion etching enabled to suggest that besides the main intercalation reaction, from Li0.5NbO2 to LiNbO2, about 9.3% of LiNbO2 undergoes a conversion reaction to Nb.

Crystalline Sb or Bi in amorphous Ti-based oxides as anode materials for sodium storage

A simple synthesis has been developed for watermelon-like nanocomposites with Ti-based oxides as the matrix. Using the case of Sb nanocrystals in amorphous TiPOx as an example, in-situ/ex-situ techniques, first-principle calculations and control experiments confirm that the formation of Ti-based oxides promotes the reduction of Sb3+ to Sb by NH3 at an elevated temperature. A similar synthesis process also succeeds for Sb nanocrystals in amorphous TiO2 and for Bi nanocrystals in amorphous TiPOx, confirming the promising potential of this synthesis. More importantly, the nanocomposite composed by crystalline Sb in an amorphous TiPOx matrix, as the anode material for sodium storage, concurrently exhibits a long cycle life (~1000 cycles) and a high capacity retention (~82%), suggesting the advantages of watermelon-like structures.