Mesoporous anatase TiO2 mesocrystal for high-performance photocatalysis and lithium-ion batteries

Mesocrystals, with their unique structures composed of aligned nanocrystals, hold promise for energy conversion and storage applications. This study presents a novel approach to synthesizing platelike mesoporous anatase TiO2 mesocrystals from non-porous H1.07Ti1.73O4·nH2O (HTO) precursors. The synthesis involves solvothermal, acid, and heat treatments, starting with the formation of a BaTiO3/HTO (BT/HTO) nanocomposite via topochemical conversion. Subsequent selective acid leaching and controlled heat treatment at 700-900 °C produced mesoporous anatase TiO2 mesocrystals with a high specific surface area and mesoporosity. These mesocrystals exhibited outstanding photocatalytic activity, achieving a surface-specific degradation efficiency of methylene blue surpassing that of commercial P25. As an anode material for lithium-ion batteries, the mesocrystals delivered an exceptional initial discharge capacity of 667.5 mA h g-1 and maintained a reversible capacity of 243.1 mA h g-1 after 100 cycles at 100 mA g-1. The enhanced performance is attributed to their optimized mesoporosity, crystallinity, and nanostructural alignment. This study advances the understanding of mesocrystal synthesis and underscores the potential of mesoporous anatase TiO2 mesocrystals in sustainable energy and environmental applications.

Mesocrystalline Effect in NiTiO3/TiO2 Nanocomposite for Enhanced Capacity of Lithium-ion Battery Anode

H2O2-modified layered titanate H1.07Ti1.73O4 (H2O2-HTO) is an excellent precursor for topochemical synthesis but its exfoliation reaction is unclear. Herein, we reported the first study on the exfoliation reaction of H2O2-HTO...

Solvothermal Reaction and Piezoelectric Response of Oriented KNbO3 Polycrystals

KNbO₃ (KN) piezoelectric polycrystals were prepared by a two-step solvothermal reaction process with the managed organic solvents as reaction mediums at a low temperature for a short time. In the solvothermal reaction system, the formation mechanism of polycrystalline KN is mainly the dissolution-deposition mechanism. The influences of alkalinity, viscosity, and the polarity for reaction mediums on the formation of the niobates were investigated. The chemical reaction mechanisms of niobate products and formation mechanism of niobate crystals from the precursor were clarified. The regulating and controlling mechanism of the phase compositions, the morphologies, and the lattice constants for the niobates obtained in varied reaction mediums were revealed. The obtained KN piezoelectric polycrystals are constructed from oriented KN nanocrystals. Piezoelectric hysteresis loops of cuboid KN polycrystals were detected for the first time. A prepared cuboid KN polycrystal shows an average d₃₃* value of 32 pm/V. The study provides a strategy for the development of oriented KN piezoelectric materials to apply the orientation engineering.

The role of cations in hydrothermal synthesis of nonlinear optical sodium niobate nanocrystals

The usability of the alkali niobates with their ferroelectric and photorefractive properties could be expanded if the development of synthesis methods would allow to obtain small, preferably monodispersed, crystals in the sub-μm to nanometer regime. Of all the possible synthesis methods, the most reliable is currently hydrothermal synthesis to generate small crystallite sizes of these materials. Although the products of sodium niobate are polydisperse and partially agglomerated, they show a significant SHG signal that is unexpectedly comparable to that of potassium niobate. A view on the hydrothermal synthesis of sodium niobate reveals that the incorporation of cations in the crystalline lattice of the niobium educt plays a part in the formation of the product. The occurrence of distinct different phases, as in the case of potassium niobate, is not observed. Instead, it is shown that a clear assignment of the crystalline phase cannot be made here. This indicates that crystallization of the alkali niobates in hydrothermal synthesis depends on the stoichiometry, the niobium starting material and the cation used.

Ferroelectric mesocrystalline BaTiO3/BaBi4Ti4O15 nanocomposite: formation mechanism, nanostructure, and anomalous ferroelectric response

Ferroelectric mesocrystalline nanocomposites are promising materials for the enhancement of ferroelectricity via lattice strain engineering due to their high density of heteroepitaxial interfaces. In the present study, a ferroelectric mesocrystalline BaTiO3/BaBi4Ti4O15 (BT/BBT) nanocomposite was synthesized using the layered titanate H1.07Ti1.73O4via a facile two-step topochemical process. The BT/BBT nanocomposite is constructed from well-aligned BT and BBT nanocrystals oriented along the [110] and [11-1] crystal-axis directions, respectively. Lattice strain is introduced into the nanocomposite through the formation of a BT/BBT heteroepitaxial interface, which results in a greatly elevated Curie temperature for BBT in the range of 400 °C to 700 °C and an improved piezoelectric response with . In addition, the BT/BBT nanocomposite is stable up to a high temperature of 1100 °C; therefore, mesocrystalline ceramics can be fabricated as high-performance ferroelectric materials.